Endometriosis is a common condition with a varied phenotype. Symptomatic cases have been associated with progesterone resistance and dysregulated cytokine production in both ectopic and eutopic endometrium. In at least some cases, this seems to be associated with chronic local inflammation and antibody self-reactivity. Coexistence of endometriosis with autoimmune disease has been documented in a small number of cases, and the presence of autoreactive antibodies in the serum of some patients with endometriosis is commonly reported. This paper briefly reviews the association between endometriosis and autoimmune disease and describes the potential role of inflammation in the development of immunologic self-reactivity in these patients.