The CYP17 gene codes for the cytochrome P450c17a enzyme, which mediates two key steps in sex steroid synthesis In this study, the association between CYP17 polymorphism and the risk of prostate cancer in comparison to benign prostatic hyperplasia (BPH) in a north Indian population was investigated.This study included 157 prostate cancer patients and 170 BPH patients as controls. A 451-bp fragment encompassing the polymorphic site was amplified by PCR and treated with the restriction enzyme MspA1. The undigested allele was recognized as A1 and the MspA1-digested variant allele was designated as the A2 allele.Men with the A2/A2 CYP17 genotype had an increased risk of prostate cancer (OR=3.56; 95% CI=1.49-8.53; p=0.004) compared with those with the A1/A1 genotype. A significantly increased risk of prostate cancer was also found in smokers as well as non-vegetarians by four-fold as compared to their counterparts. There was a significant association between the CYP17 genotype and the tumour status (stage) of prostate cancer. The A2 allele showed a 1.90- (95% CI=1.09-3.32; p=0.02) and a 1.51- (95% CI=1.08-2.13; p=0.017) fold increased risk of prostate cancer in localized and metastatic prostate cancer cases respectively.The A2 allele of the CYP17 polymorphism is associated with an increased risk of prostate cancer and has a role in the development of prostate cancer in smokers and non-vegetarians.