Trinucleotide repeats CAG(n) in androgen receptor gene is thought to be a potential site of genetic susceptibility to polycystic ovary syndrome (PCOS). However, previous studies of PCOS have shown variable association of CAG(n )polymorphism with PCOS. In order to evaluate CAG(n )polymorphism in Chinese women with PCOS, we have genotyped CAG(n) repeat numbers in female Chinese subjects (148 PCOS patients and 104 control subjects). The mean CAG(n) repeat lengths of PCOS patients and control subjects were similar (22.88 +/- 1.76 vs. 22.85 +/- 1.60; P = NS). No difference in the mean CAG(n) repeat lengths of hyperandrogenic and nonhyperandrogenic subgroups of PCOS patients was found (22.86 +/- 1.68 vs. 22.91 +/- 1.84; P = NS). Moreover, no difference was found in the term of mean CAG(n) repeat lengths in the nonhyperandrogenic subgroup and the control subjects (22.86 +/- 1.68 vs. 22.85 +/- 1.60; P = NS). However, mean CAG(n) repeat lengths were negatively correlated with serum total cholesterol and low-density lipoprotein-cholesterol concentration in PCOS patients (r = -0.182, P < 0.05 and r = -0.210, P < 0.05, respectively), but not with total testosterone, body mass index, waist and hip circumferences. The CAG(n) repeat length polymorphism may not be a major determinant of PCOS, but it may influence the lipid metabolism of PCOS patients.