To evaluate the relationships between genetic polymorphisms of the GSTs (GSTM1 and GSTT1) and cervical cancer, the null genotype of each gene was studied in squamous cell cervical cancer (SCCA) patients (n=90) and controls (n=94) in Northeast Thailand. The prevalence of the GSTM1-null genotype in the controls and SCCA patients was 59.6% and 60.0%, respectively, whereas those of the GSTT1-null genotype in the control and SCCA patients was 40.4% and 46.7%, respectively. Neither of the GST-null genotypes increased the risk for SCCA (p>0.05); however, the combination of the GSTM-1 and GSTT1-null genotypes showed a non-significant trend for an increased risk for developing cervical cancer with an adjusted OR of 2.7 (95%CI=0.8-9.0, p=0.10). Genetic polymorphisms of GSTM1 and GSTT1 were not significant risk factors for cervical cancer in either tobacco-smokers or non-smokers. A different contribution of the GST genotype to cancer risk may be attributed to a different, as yet undefined, property of the enzymes.