Polycystic ovary syndrome (PCOS) is a heterogeneous disease with a strong genetic origin, but the specific determinants are still unknown. The aim of this study was to investigate the association between the (TTTA) n polymorphism in intron 4 of CYP19 and the PCOS risk in a Chinese population. We performed a case-control study which involved 222 PCOS patients and 281 controls. The fluorescent-labeled target DNA fragments containing the (TTTA)n short tandem repeats were obtained by PCR, thereafter genotyped via capillary electrophoresis. Representative alleles were directly sequenced to confirm their repeat numbers. Genotype analysis revealed seven different alleles including 7-3(∆)-, 7-, 8-, 10-, 11-, 12- and 13-TTTA-repeats. The most common allele in a Chinese population is (TTTA) 11 in our study (0.354 for PCOS and 0.390 for controls). PCOS patients showed a higher frequency of short alleles compared with controls (0.47 vs. 0.41, OR=1.245, 95% CI 0.97-1.60). The overall allelic distributions of this polymorphism did not show any significant differences between PCOS patients and the control group. No statistical differences were found in the clinical parameters or serum steroid hormone levels among PCOS patients with different genotypes. In conclusion, PCOS patients had a higher frequency of short alleles, albeit this might not strongly affect the risk of PCOS.