The luteal phase of 20 infertile women with endometriosis who were treated with danazol (600 mg daily for 6 months) was studied by basal body temperature, plasma progesterone (P), oestradiol (E2) and prolactin (PRL) determination, and endometrial biopsy, in any one of the first three cycles after discontinuation of danazol. All endometrial specimens were noted to be fundal samples and were clearly progestational after danazol therapy. Abnormal secretory phases were detected in three patients, as in the pre-danazol control cycles. Moreover, plasma levels of P, E2 and PRL in post-danazol cycles were similar to those found in control cycles and fell within the normal range in all cases except for one patient having hyperprolactinaemia. In conclusion, our study shows that endometrial inadequacy is not the cause of the increased fetal wastage previously reported among proximally conceived pregnancies after danazol therapy for endometriosis.