Objective: To assess azathioprine-induced bone marrow toxicity and its correlation with thiopurine methyltransferase (TPMT) mutation in liver transplant patients who develop myelosuppression while on azathioprine therapy. Results: A total of 76 liver transplant patients were tested for TPMT mutation. Prevalence of TPMT mutation in the study patients was 3.95%. The heterozygous TPMT*1/*3C genotype was traced in 2.63% of the patients while 1.32% of patients were homozygous for TPMT*3C allele. Interestingly 43.4% of patients with wild allele also showed azathioprine-induced myelosuppression. Azathioprine dose of 100 mg showed a higher degree of myelotoxicity than lower doses. Haematological indices of 42.1% of patients normalised on cessation of azathioprine therapy. Methods Conclusion:Myelosuppression following the introduction of azathioprine was observed in patients with both 'mutant' and 'wild-type' alleles. Therefore a cautious approach has to be taken in pre-screening liver transplant recipients for TPMT allele determination in our population. The absence of TPMT mutation does not ensure freedom from myelosuppression. Hence regular monitoring of haematological indices of such patients receiving thiopurine therapy should be continued.