Abstract. Background: Glutathione S-transferase M1

enzymes involved in the metabolism of xenobiotics and whose polymorphisms have been related to individual cancer risks. Patients and Methods: A case-control study was performed including 92 colon, 75 lung and 23 bladder cancer patients and 121 corresponding controls to verify the existence of an association between the main genetic polymorphisms of GSTM1 and NAT2 and the risk to develop cancer. Genomic DNA, isolated from 5 mL whole blood, was used to study GSTM1 and NAT2 polymorphisms using multiplex PCR and a PCR-RFLP technique, respectively. Results: GSTM1 homozygous null genotype was associated with an increased risk of colon cancer, especially in females and in younger patients. For NAT2 gene, the results suggest a role for the low acetylator phenotype in the development of colon and lung cancer, especially in females. In bladder cancer patients two rare NAT2 genotypes were foun