The frequency of GSTM1 and GSTT1 null genotypes was 59.5% and 20.8%, respectively, in CML group, and 59.2% and 20.9%, respectively, in the control group (P value = 0.94 and 0.99, resp). This evidence concerns the gene GSTM1 and chronic myelogenous leukemia, BCR-ABL1 positive.