BACKGROUND The prostate cancer is a slowly progressing disease that begins decades prior to diagnosis. It has been suggested that there might be differences in susceptibility due to genetic polymorphisms in biotransformation enzyme genes. In the present work, associations between CYP1A1(Msp1), GSTM1(−/−) polymorphisms, and prostate cancer were analyzed in a case‐control study. METHODS Genomic DNA was isolated from peripheral blood samples, collected on EDTA. PCR‐RFLP was used to determine simultaneously Msp1 and GSTM1(−/−) polymorphisms. RESULTS In cancer patients, frequency of m2 variant allele (0.377) and GSTM1(−/−) (0.362) showed statistically significant increases compared to the control group (0.262 and 0.227, respectively). The estimate relative risks (OR) were higher for individuals carrying combined CYP1A1 and GSTM1 rare genotypes, in relation to individuals carrying CYP1A1 or GSTM1 alone. Multivariate logistic regression analysis including confounding factors (age, digital examination, and PSA antigen) showed even higher risk for individuals carrying m2m2 genotype (OR = 3.99; 95% CI, 1.27–12.54), GST(−/−) genotype (OR = 2.75; 95% CI, 1.31–5.79), and m2m2/GST(−) genotype (OR = 16.63; 95% CI, 1.67–165.48). CONCLUSIONS Taken together, these findings suggest that Chilean people carrying single or combined GSTM1 and CYP1A1 polymorphisms are more susceptible to prostate cancer. Prostate 57: 111–117, 2003. © 2003 Wiley‐Liss, Inc.