1 the pubertal response group of patients who had 5 IU/L peak LH levels in the GnRH stimulation test, and the prepubertal response group of patients who had LH levels <5 IU/L. Chronological and bone ages, height, weight, body mass index, gonadotropin response to GnRH stimulation, and basal levels of LH, fol- licle-stimulating hormone, and estradiol were studied in both groups. The relationship between basal LH and peak-stimulated LH was evaluated using Spearman's correlation. To determine the optimal cut-off val- ues of basal LH levels for differentiating between two groups, the receiver operating characteristic (ROC) curves were analyzed. Results: When the correlation between basal LH levels and peak LH after GnRH stimulation was analyzed in all subjects (N=90), basal LH levels had a statistically significant positive correlation with peak stimulated LH levels (rs=0.493, p<0.001). The cut-off level of optimal basal LH was 0.1 IU/L, according to the ROC curves. Its sensitivity was 73.3%, and its specificity was 77.8%. Conclusion: The study results showed that serum basal LH levels are useful for screening CPP in girls.