Endometriosis is a chronic, recurring condition that occurs during the reproductive years. It is characterized by endometrial tissue developing outside the uterine cavity. This endometrial tissue development is dependent on oestrogen produced primarily by the ovaries and, therefore, traditional management has focused on ovarian suppression. In this review we considered the role of modulation of the immune system as an alternative approach. This is an update of a Cochrane Review previously published in 2009 (Lu 2009).