How do I remove duplicate records in a join table in PostgreSQL?

I have a table that has a schema like this: create_table "questions_tags", :id => false, :force => true do |t| t.integer "question_id" t.integer "tag_id" end add_index "questions_tags", ["question_id"], :name => "index_questions_tags_on_question_id" add_index "questions_tags", ["tag_id"], :name => "index_questions_tags_on_tag_id" I would like to remove records that are duplicates, i.e. they have both the same tag_id and question_id as another record. What does the SQL look like for that?