Objectives: The CYP19 gene encodes aromatase-a key enzyme involved in the conversion of androstenedione/testosterone to estrone/estradiol. In this study, we analyzed the association between the TCT insertion (Ins)/deletion (Del) and TTTA repeat polymorphisms of CYP19 and prostate cancer (PCa). Methods: Automated sequencer with GeneScan software was used to determine the CYP19 gene polymorphisms in peripheral blood mononuclear cell DNA from 244 patients with PCa and 261 age-matched healthy male controls. The distribution of Stage I to IV was 3.4%, 23.8%, 19.6%, and 53.2%, respectively. The Gleason score was 2 to 5 in 22.9%, 6 to 7 in 53.2%, and 8 to 10 in 23.8%. Results: The frequency of the TCT Del/Del genotype in the Taiwanese patients with PCa (12.3%) was significantly greater than that in the controls (5.4%; P = 0.015, odds ratio [OR] 2.43, 95% confidence interval [CI] 1.23 to 4.80). Individuals with a homozygous A1 (seven TTTA repeats) genotype had a significantly greater risk of developing PCa (OR 1.59, 95% CI 1.04 to 2.44, P = 0.044). The frequency of the Ins-A6 (12 TTTA repeats) haplotype was significantly greater in the control group than in the patient group (9.8% versus 6.1%, OR 0.61, 95% CI 0.38 to 0.97). The OR of developing PCa for men with the homozygous Del-A1 diplotype was 2.31 (95% CI 1.10 to 4.83). Conclusions: The results of our study have shown that the CYP19 TCT Del/Del genotype might be a susceptibility marker for PCa. Men with the Ins-A6 haplotype had a lower risk of developing PCa.