BACKGROUND: There have been many studies on the association between the glutathione S- transferase (GST) genotype and the susceptibility to acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and the results are still controversial. We tested whether the homozygous null genotype of GST mu 1 (GSTM1) and GST theta 1 (GSTT1) genes influences the risk for MDS and AML. METHODS: We analyzed bone marrow DNA samples from 54 patients with AML or MDS (14 de novo AML, 7 secondary AML, and 33 MDS) and peripheral blood DNA samples from 75 cancer-free controls. The GSTM1 and GSTT1 genotypes were analyzed by multiplex polymerase chain reaction (PCR). RESULTS: The frequencies of GSTM1 null and GSTT1 null were not significantly increased in AML/MDS cases compared with those in controls. CONCLUSION: Our data suggest that GSTM1 and GSTT1 null genotypes may not predispose to AML/MDS in Korean population.