Acute lymphoblastic leukaemia (ALL) is the most common pediatric malignancy worldwide. The origin ofthis disease may be explained by a combination of genetic and environmental factors. Glutathione-s-transferasesare a multi-gene family of enzymes involved in the detoxification of a wide variety of environmental carcinogens.A total of 92 immunophenotyped cases (below 25 years of age) and 150 cord blood controls were here analysedby PCR for GSTM1(Present/Null) and RQ-PCR allelic discrimination assay for GSTP1(Ile105Val). We found asignificant increased risk for ALL with the GSTM1 null genotype (OR: 1.96, 95%CI=1.08-3.57), but no significantrisk was found with the GSTP1 (Ile/Val) genotype (OR: 1.32, 95%CI = 0.74-2.37) and the GSTP1 Val/Val genotype(OR: 1.41, 95%CI=0.5-3.96) alone. Combined analysis of GSTM1 and GSTP1 showed significant higher riskassociated with the GSTM1 (null/null) and GSTP1 [(Ile/Val)/ (Val/Val)] genotype (OR=2.78: 95%CI=1.16-6.69).