Cytochrome P450 2E1 and GSTM1 play major roles in metabolic activation and detoxification of many carcinogensand polymorphisms in the encoding genes have been reported to be individually associated with increased susceptibilityto certain cancer. In the present study, we investigated the RsaI, PstI and DraI polymorphisms of the CYP2E1 geneand the null GSTM1 genotype in a Thai population. DNA samples from 485 individuals were analysed by polymerasechain reaction with restriction fragment length (PCR/RFLP). The frequency of RsaI and PstI predominanthomozygous alleles (c1/c1) was 73.2%, heterozygous allele (c1/c2) was 25.6% and rare homozygous allele (c2/c2)was 1.2%. For the DraI polymorphism, the frequency of the predominant allele (DD) was 59.6%, heterozygous (CD)was 40% and rare allele (CC) was 0.4%. The frequency of GSTM1 null genotype was 62.7%. The distribution andfrequencies of these alleles showed different pattern from those found in Caucasian and some other Asian populations.With the large population in this study, we believed that our results are reliable estimates of the frequencies of thepolymorphic CYP2E1 and GSTM1 alleles in Thai population and should provide a base for further epidemiologicalstudies on their links with cancer development.