Objective: To determine the cutoff value of clomiphene citrate challenge test(CCCT) that can predict the normal and abnormal(diminished) ovarian response group and to assess the usefulness of CCCT as a predictor of ovarian reserve. Materials and Methods: From March 1994 to Februry 1996, CCCT was performed to 129 infertile patients and among them, 20 patients whose basal FSH on the third day of menstrual cycle was more than 20 mIU/ml were excluded. At the same time, the same CCCT was performed to the fifteen healthy volunteers with proven fertility to determine the cutoff value of CCCT. Results; 1) A FSH value higher than 23.4 mIU/ml, measured on the 10th day of menstrual cycle, was defined as a abnormal ovarian response. The cutoff value of 23.4 mIU/ml is more than 2 standard deviations(SD) above the mean value of 15 healthy women after CCCT. 2) The abnormal CCCT group, the subpopulation with a FSH value of 23.4 mIU/ml or more, was 7.3%(8/109) and their mean age was higher than the normal CCCT group($36.5{pm}4.5$ vs. $32.9{pm}4.8$, P = 0.059). And the percentage of the patients older than 35 years of the abnormal CCCT group was significantly higher than that of the normal CCCT group(62.5% vs. 38.6%, p <0.05). 3) There was no correlation between the hormone values of the third day and the 10th day of menstrual cycle before and after CCCT except between FSH of the third day and the 10th day. Conclusion: The CCCT is a good method to predict the individual ovarian response to COH for ART, especially in the patients who has no other abnormal findings that predict poor prognosis. And it is neccessary to determine the cutoff value of CCCT by the large numbers of randomized study, and combining the previously proven prognostic factors, it can be applicated in many individual centers for evaluate the ovarian response before ART program.