We investigated the possibility that human granulosa cells from the cumulus mass obtained during human in vitro fertilization/embryo transfer (IVF/ET) might be useful for screening of potential reproductive toxicants in vitro. The cumulus granulosa cells detached from the zona pellucida after fertilization were allowed to spontaneously adhere to the incubation dish following transfer (removal) of the embryo. These cumulus cells survived in culture for at least four additional days, appeared on simple inspection to be morphologically normal luteinized granulosa cells, and produced large amounts of progesterone (P) over the culture interval. Production gradually declined during culture in the absence of human chorionic gonadotropin (hCG); however, inclusion of hCG (100 ng/mL) in the medium maintained P production at control (day 1) levels. Introduction of estrogenic agents previously shown to suppress P production in porcine or human culture systems using mural granulosa cells showed comparable effects in this human cumulus cell system. 17 beta-estradiol (10(-5) M), clomiphene citrate (10(-5) M), and o,p-DDT (10(-5)) significantly inhibited hCG-supported P production by human cumulus cells in vitro. This system has the advantages that (1) human cumulus granulosa cells are readily available from IVF/ET programs, (2) the techniques for maintaining the cells in culture are extremely simple, (3) a marker of highly differentiated granulosa cell function (P production) can be reliably measured, and (4) the cells respond predictably like other comparable granulosa cell systems. We conclude that human cumulus cells are a readily available and useful resource for in vitro screening of potential female reproductive toxicants.