The twelfth season of the American fictional drama television series ER first aired on September 22, 2005 and concluded on May 18, 2006. The twelfth season consists of 22 episodes.
|Episode Runtime||00 Hours 45 Minutes|
|Episode Count On Season 12|
|Production Companies||Hands Down Entertainment, Constant c Productions, John Wells Productions, Amblin Entertainment, Warner Bros. Television, Amblin Television|