BACKGROUND In previous studies, higher progesterone secretion was observed in mature versus immature cumulusoocyte complexes. In mature cumulus mass that become homogeneously spread in culture (type C/D) progesterone secretion was higher than in partially (type B) or totally (type A) aggregated morphology. In sharp contrast, estradiol-17 beta secretion was significantly higher in type A than type C/D cumulus. OBJECTIVE Our purpose was to assess whether the decreased estradiol-17 beta level in type C/D cumulus culture is caused by deficiency of substrates. METHODS The different cumulus types were incubated with or without 10(-7) M dehydroepiandrosterone, 4-androstane-3, 17-dione, or testosterone. The levels of estradiol-17 beta, testosterone, and progesterone, were measured after 24 hr of culture. RESULTS The addition of dehydroepiandrosterone or 4-androstane-3, 17-dione significantly increased the estradiol-17 beta levels in all types of cumulus cells, whereas the addition of testosterone was less effective. In all types of cumulus cells the testosterone levels increased significantly on adding these androgen substrates. In the type C/D cumulus, the testosterone increased to lower levels compared to type A cumulus cells. In the presence of these androgens progesterone secretion is significantly reduced in type A cumulus cells. In type C/D cumulus cells, however, progesterone levels were significantly higher than in type A. The estradiol-17 beta/ testosterone and progesterone/estradiol-17 beta ratios, which partially resemble the degree of aromatase activity and the degree of selectivity for progesterone secretion, respectively, were higher in type C/D than in type A cumulus cells. CONCLUSIONS In type C/D cumulus the significant increase in estradiol-17 beta secretion in the presence of various androgens suggests that, under basal conditions, androgen is less available for estradiol-17 beta biosynthesis compared to type A cumulus. Furthermore, the higher progesterone secretion in type C/D cumulus may suggest that the follicles yielding type C/D cumulus cells are more mature than the follicles yielding type A cumulus.