Follicular fluid(FF) prostaglandin $E_2$(PG$E_2$) and $PGF_{2{alpha}}$ levels were compared in 3 groups of spontaneously ovulatory women undergoing ovulation induction with clomiphene citrate (CC) alone or with human menopausal gonadotropin(hMG) (14 patients), hMG(9 patients), or pure FSH/hMG(11 patients) for the purpose of in vitro fertilization. FF volume aspirated did not differ significantly according to the maturity of the oocyte. According to hyperstimulation regimens, the volume of FF from which preovulatory occytes were obtained was significantly less in the hMG-treated group than in the other groups. In follicles of preovulatory oocytes, FF PG$E_2$ values were significantly lower in the FSH treated group than in the Cc.treated or hMG-treated group, and FF $PGF_{2{alpha}}$ values were significantly higher in the hMG-treated group than in the CC-treated or FSH-treated group. In follicles of immature or atretic oocytes, there was no significant difference in FF PG$E_2$ and PG$F_{2{alpha}}$ concentrations of the similar morphology of the oocyte according to hyperstimulation regimens. In all cycles, FF PG$E_2$ and PG$F_{2{alpha}}$ values of preovulatory oocytes were not significantly different from those of immature oocytes, but those of atretic oocytes were relatively lower than those of fertilizable oocytes and it was statistically signifincant in PG$E_2$ values of CC-treated group. In all treatment groups, FF PG$E_2$ and PG$F_{2{alpha}}$ levels did not show and close relationship with the success of fertilization in vitro and of pregnancy after embryo transfer. Above results suggested that FF PG$E_2$ and PG$F_{2{alpha}}$ be involved in oocyte maturation and ovulation, but their relationship with the success of in vitro fertilization was not found.