diff --git a/db/migrate/20140818195821_remove_institution_from_user.rb b/db/migrate/20140818195821_remove_institution_from_user.rb
new file mode 100644
index 0000000..37486cd
--- /dev/null
+++ b/db/migrate/20140818195821_remove_institution_from_user.rb
@@ -0,0 +1,9 @@
+class RemoveInstitutionFromUser < ActiveRecord::Migration
+  def up
+    remove_column :users, :institution_id
+  end
+
+  def down
+    add_column :users, :institution_id
+  end
+end
diff --git a/db/migrate/20140818200738_create_institution_user_relation_table.rb b/db/migrate/20140818200738_create_institution_user_relation_table.rb
new file mode 100644
index 0000000..7068d72
--- /dev/null
+++ b/db/migrate/20140818200738_create_institution_user_relation_table.rb
@@ -0,0 +1,12 @@
+class CreateInstitutionUserRelationTable < ActiveRecord::Migration
+  def up
+    create_table :institutions_users do |t|
+      t.belongs_to :user
+      t.belongs_to :institution
+    end
+  end
+
+  def down
+    drop_table :institutions_users
+  end
+end
diff --git a/lib/ext/user.rb b/lib/ext/user.rb
index ed8face..9314624 100644
--- a/lib/ext/user.rb
+++ b/lib/ext/user.rb
@@ -2,7 +2,7 @@ require_dependency 'user'
 
 class User
 
-  belongs_to :institution
+  has_and_belongs_to_many :institutions
 
   validate :email_different_secondary?, :email_has_already_been_used?,
            :secondary_email_format, :email_suffix_is_gov?
diff --git a/lib/institution.rb b/lib/institution.rb
index 930cd3a..159eafc 100644
--- a/lib/institution.rb
+++ b/lib/institution.rb
@@ -5,7 +5,7 @@ class Institution < ActiveRecord::Base
   attr_accessible :name, :acronym, :unit_code, :parent_code, :unit_type, 
                   :juridical_nature, :sub_juridical_nature, :normalization_level, 
                   :version, :cnpj, :type, :governmental_power, :governmental_sphere
-  has_many :users
+  has_and_belongs_to_many :users
 
   validates :name, :presence=>true, :uniqueness=>true
 
diff --git a/lib/institutions_users.rb b/lib/institutions_users.rb
new file mode 100644
index 0000000..e47da86
--- /dev/null
+++ b/lib/institutions_users.rb
@@ -0,0 +1,4 @@
+class InstitutionUser < ActiveRecord::Base
+  belongs_to :user
+  belongs_to :institution
+end
--
libgit2 0.21.2