This study was designed to assess the effect of long-term treatment with three combined oral contraceptives (OC) on the gonadotropin response to LHRH. The release of LH and FSH after a single 50-μg dose of LHRH was studied from Days 11 to 14 of treatment and Days 2 and 3 after discontinuation of the treatment. The responses were compared with controls during the luteal phase (Days 16 to 19) of the menstrual cycle. LH and FSH baseline levels and release after LHRH injection were markedly depressed in women on OC treatment. The patterns of gonadotropin response after LHRH, however, were similar to the responses during the luteal phase. Following discontinuation of OC treatment, the basal levels of LH and FSH and the response to LHRH continued to be depressed, with a further decrease in the FSH release. These results indicate that treatment with combined OC exert a significant depression on the release of gonadotropins.