Allogeneic stem cell transplant (ASCT) recipients have severely impaired cell-mediated immunity as a result of their conditioning regimen, immunosuppressive therapy, and graft-versus-host disease (GVHD). Accordingly, they are susceptible to bacterial, viral, and fungal infections. Mycobacterial infections can also occur in these patients, although the incidence is not high, even in countries where tuberculosis (TB) is common. We describe four patients from our hospital who developed pulmonary T tuberculous infection in the post-transplant period over a 3-year period. During that time a total of 127 patients have undergone an ASCT, representing an incidence of TB of 2.3%. The pretransplant diagnosis was acute myeloid leukemia in three patients and chronic myeloid leukemia in one case. All four patients were treated with a combination of cyclosporine and corticosteroids for acute and/or chronic GVHD. Three of the four patients were born outside Australia, each from an area where TB is endemic. Two patients died within 2 weeks of the commencement of antituberculous therapy, the third is alive and well, and the fourth died of multi-organ failure and sepsis after 4 months in hospital. A higher index of suspicion of previous TB exposure and infection is required in the assessment of ASCT recipients, particularly in those born in areas where TB is common or endemic.