Colorectal cancer is a major cause of morbidity and mortality both globally and in Iran. The aim of this study was to determine the association between genetic polymorphisms of glutathione S-transferases P1, M1 and T1 (GSTP1, M1, T1) and susceptibility to colorectal cancer (CRC). Genotyping of GSTP1, GSTM1 and GSTT1 was performed by the use of pyrosequencing. One hundred cases and healthy controls were enrolled into this study. Mean GSTT1 polymorphism type was significantly (P < 0.01) higher in cases as compared to controls (P < 0.0001: OR, 2.43: 95% CI, 1.47-4). On the other hand there is no significant association between GSTM1, GSTP1 and colorectal cancer. GSTs measurement may be useful as a colorectal marker in colorectal cancer and biopsies obtained at colonoscopy can be used to measure tumor markers.