Abstract. Deletion polymorphisms for the glutathione S-transferase (GST) gene are associated with increased risk of cancer, and are implicated in detoxifying mutagenic electrophilic compounds. GST Polymorphic variants were reported for different populations. The aim of this study was to investigate the frequencies of GSTM1 and GSTT1 null genotypes among Bahraini, Lebanese and Tunisian Arabs. GST genotyping was done by multiplex PCR-based methods. Study subjects comprised 167 Bahrainis, 141 Lebanese and 186 Tunisians unrelated healthy individuals. GSTM1 deletion homozygosity of 49.7%, 52.5% and 63.4% were recorded for Bahraini, Lebanese and Tunisians, respectively. Among Bahrainis, the prevalence of GSTT1 null homozygotes was 28.7%, while in higher rates were seen in Lebanese (37.6%) and Tunisians (37.1%). Our results indicate that there are no major differences in allelic distribution of GSTM1 and GSTT1 genes between the three Arab populations investigated except between Bahrainis and Tunisians regarding the allelic distribution of GSTM1 gene (P = 0.013). Combined analysis of both genes revealed that 14.4% of Bahrainis, 16.3% of Lebanese and 21.0% of Tunisians harbor the deleted genotype of both genes. This is the first study that addresses GST gene polymorphism in Bahraini and Lebanese Arabs, and will help genetic studies on the association of GSTM1 and GSTT1 polymorphisms with disease risks and drug effects in Arab populations.