Porcine follicular fluid (pFF) contains a nonsteroidal factor(s) that modifies pituitary secretion of both FSH and LH under certain physiological and experimental conditions. The aim of this study was to further define the activity of pFF on basal and pulsatile gonadotropin secretion after bilateral oophorectomy in monkeys. Sexually mature female rhesus monkeys underwent bilateral oophorectomy during the early follicular phase of the menstrual cycle. For 10 consecutive days, beginning on the day of surgery, monkeys were given twice daily sc injections of 2.5 ml normal saline (group I, control; n = 3), 2.5 ml steroid-free pFF (group II; n = 3), or 5.0 ml steroid-free pFF (group III; n = 3). Blood was drawn daily for 32 days, beginning the day before castration. One day before and on days 6 and 20 after castration, monkeys were placed in a restraining chair, and blood samples were drawn every 15 min for 6 h via an indwelling venous catheter. All samples were radioimmunoassayed for FSH and LH. In group I, a significant increase in serum FSH and LH occurred on days 3 and 6 postcastration, respectively. A significant increase in serum FSH did not occur until day 13 postcastration in groups II and III. Serum LH was significantly increased on days 10 and 9 postcastration in groups II and III, respectively. The LH pulse frequency ranged from 60-105 min and did not change after castration in control or pFF-treated animals. The LH pulse increment was significantly increased on day 6 postcastration in group I, but not until day 20 postcastration in groups II and III. Only minor oscillations in FSH were found until day 20 postcastration, at which time there was no significant difference in FSH pulse frequency or increment among groups. These findings demonstrate that a nonsteroidal factor(s) in pFF suppresses basal FSH and LH concentrations and LH pulse increment in monkeys after surgical castration. Further, because LH, but not FSH, concentrations began to increase during pFF treatments, these data suggest a temporal disparity in the effects of pFF on FSH and LH secretory profiles.