In the present study we have measured the concentrations of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in preovulatory follicular fluid (FF) samples obtained from patients undergoing ovulation induction with human menopausal gonadotropin/human chorionic gonadotropin. In 13 of the 24 (54%) FF samples obtained from 20 patients, TNF-α was detected. In contrast, IL-1β was observed in none of the 16 samples assessed. In the samples with detectable levels of TNF-α, the mean concentration was 40.1 pg/ml (range 20-74 pg/ml). In addition, we found an association between the presence of TNF-α in the FF and the serum level of 17β-estradiol (E2) and progesterone (P). The E2 and P levels were significantly lower in patients with detectable levels of TNF-α in FF than in patients with no detectable TNF-α in FF. In summary, the present study shows the presence of TNF-α and the absence IL-1β in hyperstimulated human preovulatory FF. In addition, our results show an association between the presence of TNF-α in FF and low E2 and P levels in serum, suggesting a role for TNF-α in the regulation of human s