Mixed cell preparations (theca plus granulosa) prepared from the hierarchy of follicles of quails ovaries were incubated under defined conditions with or without the addition of ovine luteinizing hormone (oLH), ovine follicle stimulating hormone (oFSH), theophylline, cycloheximide, or dibutyryl cyclic adenine monophosphate (db cAMP); or in the presence of androstenedione or testosterone as aromatizable substrate. Steroids secreted into the medium during the 4-hr incubation period were assayed by radioimmunoassay. Cells from the largest follicles (F1) secreted predominantly progesterone, were stimulated by LH and db cAMP, and the response was potentiated by theophylline, but FSH had no stimulatory effect. The F1 cells showed increasing basal and LH-stimulated responses between 18 and 12 hr before the next expected oviposition. Cells from the smaller follicles (F3 and F4) secreted predominantly estrogens, and were stimulated by FSH but not by db cAMP and only to a small extent by theophylline. Addition of androstenedione (10(-7) M) or testosterone (10(-7) M) enhanced estrogen secretion, which was further raised by the simultaneous addition of FSH. These results confirm previous reports on the sites of steroid secretion within quail follicles and suggest that while the action of LH on the cells from F1 follicles may be mediated in part through the adenylate cyclase system, the action of FSH on the smaller follicles may be substantially independent of cAMP.