diff --git a/app/controllers/main_controller.rb b/app/controllers/main_controller.rb
--- a/app/controllers/main_controller.rb
+++ b/app/controllers/main_controller.rb
@@ -193,16 +193,62 @@
     end
   end
 
+  def problem_list_by_user_contests(user)
+    contest_problems = []
+    pin = {}
+    user.contests.each do |contest|
+      available_problems = contest.problems.available
+      contest_problems << {
+        :contest => contest,
+        :problems => available_problems
+      }
+      available_problems.each {|p| pin[p.id] = true}
+    end
+    other_avaiable_problems = Problem.available.find_all {|p| pin[p.id]==nil and p.contests.length==0}
+    contest_problems << {
+      :contest => nil,
+      :problems => other_avaiable_problems
+    }
+    return contest_problems
+  end
+
+  def problem_list_for_user(user, contest_problems=nil)
+    if not Configuration.multicontests?
+      return Problem.find_available_problems
+    else
+      if contest_problems==nil
+        contest_problems = problem_list_by_user_contests(user)
+      end
+
+      problems = []
+      collected = {}
+      contest_problems.each do |cp|
+        cp[:problems].each do |problem|
+          if not collected[problem.id]
+            problems << problem
+            collected[problem.id] = true
+          end
+        end
+      end
+      return problems
+    end
+  end
+
   def prepare_list_information
-    @problems = Problem.find_available_problems
-    @prob_submissions = Array.new
     @user = User.find(session[:user_id])
+    if not Configuration.multicontests?
+      @problems = problem_list_for_user(@user)
+    else
+      @contest_problems = problem_list_by_user_contests(@user)
+      @problems = problem_list_for_user(@user, @contest_problems)
+    end
+    @prob_submissions = {}
     @problems.each do |p|
       sub = Submission.find_last_by_user_and_problem(@user.id,p.id)
       if sub!=nil
-        @prob_submissions << { :count => sub.number, :submission => sub }
+        @prob_submissions[p.id] = { :count => sub.number, :submission => sub }
       else
-        @prob_submissions << { :count => 0, :submission => nil }
+        @prob_submissions[p.id] = { :count => 0, :submission => nil }
       end
     end
     prepare_announcements
diff --git a/app/models/configuration.rb b/app/models/configuration.rb
--- a/app/models/configuration.rb
+++ b/app/models/configuration.rb
@@ -106,6 +106,10 @@
     return get(SYSTEM_MODE_CONF_KEY) == 'indv-contest'
   end
 
+  def self.multicontests?
+    return get('system.multicontests') == true
+  end
+
   def self.time_limit_mode?
     mode = get(SYSTEM_MODE_CONF_KEY)
     return ((mode == 'contest') or (mode == 'indv-contest')) 
diff --git a/app/models/problem.rb b/app/models/problem.rb
--- a/app/models/problem.rb
+++ b/app/models/problem.rb
@@ -8,11 +8,13 @@
   validates_format_of :name, :with => /^\w+$/
   validates_presence_of :full_name
 
+  named_scope :available, :conditions => {:available => true}
+
   DEFAULT_TIME_LIMIT = 1
   DEFAULT_MEMORY_LIMIT = 32
 
   def self.find_available_problems
-    find(:all, :conditions => {:available => true}, :order => "date_added DESC")
+    Problem.available.all(:order => "date_added DESC")
   end
 
   def self.create_from_import_form_params(params, old_problem=nil)
diff --git a/app/views/main/_problem.html.erb b/app/views/main/_problem.html.erb
--- a/app/views/main/_problem.html.erb
+++ b/app/views/main/_problem.html.erb
@@ -7,12 +7,12 @@
     <%= link_to_description_if_any "[#{t 'main.problem_desc'}]", problem %>
   </td>
   <td align="center">
-    <%= @prob_submissions[problem_counter][:count] %>
+    <%= @prob_submissions[problem.id][:count] %>
   </td>
   <td>
     <%= render :partial => 'submission_short', 
                :locals => { 
-                 :submission => @prob_submissions[problem_counter][:submission],
+                 :submission => @prob_submissions[problem.id][:submission],
                  :problem_name => problem.name }%>
   </td>
 </tr>
diff --git a/app/views/main/list.html.haml b/app/views/main/list.html.haml
--- a/app/views/main/list.html.haml
+++ b/app/views/main/list.html.haml
@@ -22,13 +22,26 @@
   %p=t 'main.start_soon'
 
 - if Configuration.show_tasks_to?(@user)
-  %table.info
-    %tr.info-head
-      %th
-      %th Tasks
-      %th # of sub(s)
-      %th Results
-    = render :partial => 'problem', :collection => @problems
+  - if not Configuration.multicontests?
+    %table.info
+      %tr.info-head
+        %th
+        %th Tasks
+        %th # of sub(s)
+        %th Results
+      = render :partial => 'problem', :collection => @problems
+  - else
+    - @contest_problems.each do |cp|
+      %h2{:class =>'contest-title'}
+        = "#{cp[:contest] ? cp[:contest].title : 'Public problems'}"
+      %table.info
+        %tr.info-head
+          %th
+          %th Tasks
+          %th # of sub(s)
+          %th Results
+        = render :partial => 'problem', :collection => cp[:problems]
+
 
 %hr/
 
diff --git a/spec/controllers/main_controller_spec.rb b/spec/controllers/main_controller_spec.rb
--- a/spec/controllers/main_controller_spec.rb
+++ b/spec/controllers/main_controller_spec.rb
@@ -1,7 +1,107 @@
-
 require File.dirname(__FILE__) + '/../spec_helper'
 
-describe MainController do
+module ConfigHelperMethods
+  def enable_multicontest
+    c = Configuration.new(:key => 'system.multicontests',
+                          :value_type => 'boolean',
+                          :value => 'true')
+    c.save
+  end
+
+  def disable_multicontest
+    c = Configuration.new(:key => 'system.multicontests',
+                          :value_type => 'boolean',
+                          :value => 'false')
+    c.save
+  end
+end
+
+describe MainController, "when a user comes to list page" do
+
+  it "should redirect user to login page when unlogged-in user try to access main/list" do
+    get 'list'
+    response.should redirect_to(:action => 'login')
+  end
+
+end
+
+describe MainController, "when a logged in user comes to list page, with multicontests off" do
+  integrate_views
+
+  include ConfigHelperMethods
+
+  fixtures :users
+  fixtures :problems
+  fixtures :contests
+
+  before(:each) do
+    disable_multicontest
+  end
+
+  it "should list available problems" do
+    john = users(:john)
+    get "list", {}, {:user_id => john.id}
+
+    response.should render_template 'main/list'
+    response.should have_text(/add/)
+    response.should have_text(/easy_problem/)
+    response.should have_text(/hard_problem/)
+  end
+
+end
+
+describe MainController, "when a logged in user comes to list page, with multicontests on" do
+  integrate_views
+
+  include ConfigHelperMethods
+
+  fixtures :users
+  fixtures :problems
+  fixtures :contests
+
+  before(:each) do
+    enable_multicontest
+  end
+
+  it "should list only available public problems to users with no contest assigned" do
+    john = users(:john)
+    get "list", {}, {:user_id => john.id}
+    
+    response.should render_template('main/list')
+    response.should have_text(/add/)
+    response.should_not have_text(/easy_problem/)
+    response.should_not have_text(/hard_problem/)
+  end
+
+  it "should list available problems on a specific contest" do
+    james = users(:james)
+    get "list", {}, {:user_id => james.id}
+
+    response.should render_template('main/list')
+    response.should have_text(/add/)
+    response.should have_text(/easy_problem/)
+    response.should_not have_text(/hard_problem/)
+  end
+
+  it "should shows available problems by contests" do
+    james = users(:james)
+    get "list", {}, {:user_id => james.id}
+
+    response.should render_template('main/list')
+    response.should have_text(Regexp.new('Contest A.*easy_problem', Regexp::MULTILINE))
+  end
+
+  it "should shows available problems by contests; problems belonging to more the one contest should appear many times" do
+    jack = users(:jack)
+    get "list", {}, {:user_id => jack.id}
+
+    response.should render_template('main/list')
+    response.should have_text(Regexp.new('Contest A.*easy_problem.*Contest B.*easy_problem', Regexp::MULTILINE))
+    response.should have_text(Regexp.new('Contest B.*hard_problem', Regexp::MULTILINE))
+  end
+end
+
+describe MainController, "when a user loads sources and compiler messages" do
 
   before(:each) do
     @problem = mock(Problem, :name => 'test', :output_only => false)
@@ -13,44 +113,47 @@
                        :language => @language,
                        :source => 'sample source',
                        :compiler_message => 'none')
+
     @user = mock(User, :id => 1, :login => 'john')
+    @user.should_receive(:update_start_time).at_most(:once)
+
     @another_user = mock(User, :id => 2, :login => 'mary')
-  end
+    @another_user.should_receive(:update_start_time).at_most(:once)
 
-  it "should redirect user to login page when unlogged-in user try to access main/list" do
-    get 'list'
-    response.should redirect_to(:action => 'login')
+    User.should_receive(:find).
+      with(1).any_number_of_times.
+      and_return(@user)
+    User.should_receive(:find).
+      with(2).any_number_of_times.
+      and_return(@another_user)
+    Submission.should_receive(:find).
+      any_number_of_times.with(@submission.id.to_s).
+      and_return(@submission)
   end
 
   it "should let user sees her own source" do
-    Submission.should_receive(:find).with(@submission.id.to_s).and_return(@submission)
-    User.should_receive(:find).with(1).and_return(@user)
-    @user.should_receive(:update_start_time)
+    @submission.should_receive(:download_filename).and_return("foo.c")
     get 'source', {:id => @submission.id}, {:user_id => 1}
     response.should be_success
   end
 
   it "should let user sees her own compiler message" do
-    Submission.should_receive(:find).with(@submission.id.to_s).and_return(@submission)
-    User.should_receive(:find).with(1).and_return(@user)
     get 'compiler_msg', {:id => @submission.id}, {:user_id => 1}
     response.should be_success
   end
 
   it "should not let user sees other user's source" do
-    Submission.should_receive(:find).with(@submission.id.to_s).and_return(@submission)
-    User.should_receive(:find).with(2).and_return(@another_user)
     get 'source', {:id => @submission.id}, {:user_id => 2}
     flash[:notice].should =~ /[Ee]rror/ 
     response.should redirect_to(:action => 'list')
   end
 
   it "should not let user sees other user's compiler message" do
-    Submission.should_receive(:find).with(@submission.id.to_s).and_return(@submission)
-    User.should_receive(:find).with(2).and_return(@another_user)
     get 'compiler_msg', {:id => @submission.id}, {:user_id => 2}
     flash[:notice].should =~ /[Ee]rror/ 
     response.should redirect_to(:action => 'list')
   end
 
 end
+
+
diff --git a/test/fixtures/problems.yml b/test/fixtures/problems.yml
--- a/test/fixtures/problems.yml
+++ b/test/fixtures/problems.yml
@@ -4,8 +4,21 @@
   name: add
   full_name: add_full_name
   available: true
+
 two:
   id: 2
   name: subtract
   full_name: subtract_full_name
   available: false
+
+easy:
+  name: easy_problem
+  full_name: Easy Problem
+  available: true
+  contests: contest_a, contest_b
+
+hard:
+  name: hard_problem
+  full_name: Hard Problem
+  available: true
+  contests: contest_b
diff --git a/test/fixtures/users.yml b/test/fixtures/users.yml
--- a/test/fixtures/users.yml
+++ b/test/fixtures/users.yml
@@ -11,6 +11,7 @@
   full_name: john
   hashed_password: <%= User.encrypt("hello",salt) %>
   salt: <%= salt %>
+
 mary:
   login: mary
   full_name: mary
@@ -18,3 +19,16 @@
   salt: <%= salt %>
   roles: admin
 
+james:
+  login: james
+  full_name: James
+  hashed_password: <%= User.encrypt("morning",salt) %>
+  salt: <%= salt %>
+  contests: contest_a
+
+jack:
+  login: jack
+  full_name: Jack
+  hashed_password: <%= User.encrypt("morning",salt) %>
+  salt: <%= salt %>
+  contests: contest_a, contest_b
diff --git a/test/functional/main_controller_test.rb b/test/functional/main_controller_test.rb
--- a/test/functional/main_controller_test.rb
+++ b/test/functional/main_controller_test.rb
@@ -1,20 +1,4 @@
 require File.dirname(__FILE__) +  '/../test_helper'
 
 class MainControllerTest < ActionController::TestCase
-  fixtures :users
-  fixtures :problems
-
-  def test_should_redirect_new_user_to_login
-    get :list
-    assert_redirected_to :controller => 'main', :action => 'login'
-  end
-
-  def test_should_list_available_problems_if_logged_in
-    john = users(:john)
-    get :list, {}, {:user_id => john.id}
-
-    assert_template 'main/list'
-    assert_select "table tr:nth-child(2)", :text => /\(add\)/
-  end
-
 end