Serum and follicular fluid levels of CEA, CA 125 and SCC of women participating in an IVF program, in 42 cycles stimulated with GnRH-a and gonadotropins and in 26 unstimulated cycles triggered with HCG, were evaluated and compared with (a) steroid and gonadotropin levels, (b) the results of IVF, and (c) serum values in a control group of women with spontaneous normal ovulatory cycles. In the control group, serum antigens did not vary significantly during the 3 phases of the cycle. In stimulated cycles the median values in serum were 0.7 ng/ml (range, 0.0-2.1) for CEA, 14.0 U/ml (3.3-32.4) for CA 125 and 2.05 ng/ml (1.1-17.8) for SCC, whereas the median values in follicular fluid were 0.6 (0.0-27.9), 21.5 (0-670) and 21.4 (1-360), respectively. In unstimulated cycles the median values and ranges in serum were 0.9 (0.4-3.9), 12.1 (4.8-63.4) and 1.85 (0.7-4.4), respectively, whereas in follicular fluid they were 2.9 (0.4-180.7), 32 (1.7-600) and 231 (10.8-904). Different follicles of the same patients in stimulated cycles showed a wide divergence for all three antigens. In unstimulated cycles all three antigens in follicular fluid were strongly correlated and a significant inverse correlation was observed between LH and both CA 125 and SCC in serum. In either group of cycles, no significant relationship was found between any serum or follicular fluid antigen and estradiol or testosterone, pregnancy rate, or oocyte quality and fertilization. Thus, in both stimulated and unstimulated cycles follicular fluid contains CEA, CA 125 and SCC in considerable amounts while in serum only SCC was found elevated. It seems that no correlation exists between any of the three antigens and steroidogenesis or the results of the IVF-ET. © 1994.