The ability of luteal tissue from rhesus monkeys, collected from spontaneous and prostaglandin F2 alpha (PGF2 alpha) induced luteolytic cycles, to secrete progesterone in response to hCG or dibutyryl cAMP in vitro was assessed. It was expected that the corpus luteum exposed to PGF2 alpha would behave in a similar manner to the corpus luteum of normal cycles undergoing luteal regression. PGF2 alpha (10 ng microliters-1 h-1) or vehicle (1 microliter h-1) was infused into the corpus luteum from 7 days after the preovulatory oestradiol surge. Lutectomy was performed at 2, 3 and 4 days after the start of the intraluteal infusion and at menses. Luteal progesterone content was determined and the secretion of progesterone in response to hCG (10 miu ml-1) or dibutyryl cAMP (5 mmol l-) was evaluated in vitro. A third group of monkeys underwent lutectomy sequentially during the luteal phase and were grouped by luteal age from days after the preovulatory oestradiol surge: early luteal (days 4-6), mid-luteal (days 7-9), late luteal (days 10-14) and menses. Immediately before luteal excision, an ovarian venous blood sample was taken for progesterone determination. Approximately 2-5 mg of minced luteal tissue was incubated at 37 degrees C in 2 ml of Krebs-Ringer bicarbonate buffer for 2 h in the presence or absence of hCG or dibutyryl cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)