The cause of infertility has remained obscure in women with endometriosis in whom the tuboovarian relationship is unaltered. Abnormal corpus luteum function has been one mechanism implicated in the pathophysiology of endometriosis in infertilityl-3 and may also be a possible explanation for the high frequency of spontaneous abortions among women with untreated endometriosis.4 However, we have observed only an occasional occurrence of luteal phase deficiency in women with an ultimate diagnosis of endometriosis. In order to verify this observation, we examined the incidence of luteal phase defects (LPDs) in. our infertility population.