To determine the (tttta)n repeat polymorphisms at the promoter region of CYP11alpha gene, and study its linkage to hyperandrogenism of polycystic ovary syndrome (PCOS) in Chinese women, a case-control study was conducted in the Reproductive Medical Center of the Second Affiliated Hospital of Zhengzhou University (Zhengzhou, China). 96 PCOS patients and 78 healthy control women were included. CYP11alpha (tttta)n repeat-polymorphism genotyping analysis was performed by using polymerase chain reaction (PCR). Serum pituitary hormone and total testosterone levels were measured by ELISA. 4 different CYP11alpha (tttta)n allelles were identified, corresponding to 4-, 6-, 8-, and 9-repeat-unit alleles. The frequency and distribution of these alleles are 0.16, 0.33, 0.38, and 0.13 respectively in PCOS patients, as compared with 0.20, 0.34, 0.35, and 0.11 respectively in healthy controls. There were no significant differences between these two groups. Moreover, no correlation between the polymorphism of CYP11alpha gene and serum testosterone level of patients with PCOS and controls was observed. It is concluded that microsatellite polymorphism (tttta)n of gene CYP11alpha exists in Chinese women and the polymorphism of CYP11alpha gene does not play an important role in the pathogenesis of Chinese patients with PCOS, especially in patients with hyperandrogenism.