To evaluate prospectively the prognostic factors for ovulatory responses following clomiphene citrate (CC) administration in polycystic ovary syndrome (PCOS).Fifty-nine infertile patients with a diagnosis of PCOS were recruited. Ovulation was induced using 100mg/day CC administered daily from days 5 to 9 of the cycle. Endocrine and metabolic parameters between responder and non-responder groups were analyzed.For a 75-g fasting glucose load (75-g OGTT), blood glucose levels at 60 and 120min, the area under the curve (AUC) and blood insulin levels at 120min in the non-responder group (n=25) were significantly higher than those in the responder group (n=34), although the measurements of fasting blood glucose and insulin were not significantly different between the two groups. In the receiver operating characteristic curves, the most appropriate cutoff point was 120mg/dl for the blood glucose level at 120min and 9000 for the blood glucose×insulin level at 120min. There were no significant differences in the clinical characteristics or in the endocrine and metabolic parameters between conceived (n=9) and non-conceived groups (n=21).The levels of blood glucose and blood glucose×insulin at 120min after 75-g OGTT could be good biochemical markers of CC resistance in PCOS. No predictors of conception following CC therapy were identified by this study.