TAAAAn polymorphism in sex hormone-binding globulin (SHBG) gene has been found to influence the transcriptional activity of SHBG gene in vitro, and several studies have reported variable associations of this polymorphism with serum SHBG levels in women with polycystic ovary syndrome (PCOS). We have investigated the association of TAAAAn polymorphism with PCOS in 187 women with PCOS and 176 controls; in which five alleles (6-10 repeats) and 13 genotypes were found. None of the TAAAAn alleles or genotypes occurred in significant different frequency in PCOS patients compared with controls. Serum SHBG in the PCOS group was significantly lower than those in controls (33.8 +/- 30.2 nmol/l vs. 65.58 +/- 31.12 nmol/l; P < 0.01). Serum SHBG concentrations were similar for patients with PCOS whether they displayed short or long genotypes for TAAAAn (Log10SHBG: 1.46 +/- 0.38 and 1.58 +/- 0.33, respectively). Similar results were observed for controls (Log10SHBG: 1.79 +/- 0.17 and 1.77 +/- 0.14, respectively). In contrast, serum SHBG values were negatively associated with body mass index (BMI) and homeostasis model assessment of insulin resistance in the PCOS group (B = -0.285 and -0.264, respectively; P < 0.01). Thus, the TAAAAn polymorphism in SHBG gene was not a determinant of PCOS in this population of Chinese women, whereas, serum SHBG was significantly associated with BMI and insulin resistance in these PCOS patients.