CYP3A5 is an important genetic contributor to inter-individual differences in CYP3A-dependent clinically important drugs of metabolism and also of various endogenous compounds and environmental contaminants. The CYP3A5*3 allele results in a truncated protein with loss of CYP3A5 expression and CYP3A5*6 is associated with lower CYP3A5 catalytic activity. The polymorphism analysis was performed by PCR-RFLP and some representative cases by direct sequencing. Our case control study involved 183 consecutive North Indian CML patients in chronic phase of disease and 208 geographically and racially matched healthy controls. PCR-RFLP was carried out to determine the frequency of CYP3A5*3 and CYP3A5*6 genotypes. The relationship between these allelic variants and risk of CML was assessed by means of odds ratio (OR) with 95% confidence limits calculated by logistic regression. The frequencies of CYP3A5*1/*1, CYP3A5*1/*3, and CYP3A5*3/*3 genotypes in CML and controls were examined, and the quantitative comparison of the frequency distributions between CML versus control were performed, showing no significant differences among these comparison pairs (P = 0.88, 0.65, and 0.80, respectively). However, we did not find the CYP3A5*6 allele in any of the controls and leukemia patients. It is concluded that there is no association of this polymorphism with the risk of chronic myeloid leukemia.