In 24-h cultures, steroid production by cells from non-atretic follicles increased with increasing follicular diameter. Cells from atretic follicles, of all sizes, produced low amounts of oestradiol-17\g=b\, but very high amounts of progesterone, relative to cells from non-atretic follicles. Increasing the culture period to 72 h caused little change in daily progesterone and oestradiol-17\g=b\production by granulosa cells from atretic follicles. In contrast, in cells from non-atretic follicles,

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... daily progesterone production increased and daily oestradiol-17\g=b\production decreased to the levels observed with cells from atretic follicles. Dibutyryl cyclic AMP (1\m=.\0mm) significantly stimulated progesterone production by cells from atretic, but not from non-atretic, follicles. Testosterone (1 \g=m\g/ml) had no effect on progesterone production by cells from atretic follicles, while oestradiol-17\g=b\,oestrone, testosterone, androstenedione and 5\g=a\-dihydrotestosterone (0\p=n-\1000ng/ml) each significantly suppressed progesterone production by cells from non-atretic follicles in a dose-dependent manner. Morphometric analysis revealed few subcellular differences between cells from non\x=req-\ atretic and atretic follicles. Mean cell volume was significantly higher for cells from atretic compared to non-atretic follicles, but the mean volumes of the major subcellular components were not influenced by follicle health. The mean surface area of the plasma and nuclear membrane, and granular endoplasmic reticulum was also significantly higher in cells from atretic compared to non-atretic follicles.