Mycobacterium tuberculosis is a serious, but rare infectious complication after allogeneic bone marrow transplantation. Tuberculosis is a major problem in South East Asia, particularly in India and Pakistan. We describe here infection due to mycobacterium tuberculosis in four patients after allogeneic stem cell transplantation (Allo SCT). The diagnosis was made on the bases of clinical findings, sputum / blood / pleural and pericardial fluids / broncho alveolar lavage (BAL) and tissue biopsy examination. Anti tuberculosis therapy (ATT) was started immediately after diagnosis. Three patients responded to antituberculosis therapy, where as one patient developed severe infective respiratory complications and died at six months post transplant. Mycobacterial infection should be considered in patients post allo SCT with unexplained fever, cough or pleuritic chest pain. These patients at diagnosis should be promptly treated with ATT.