In general, tuberculosis (Tb) is rarely seen in allogeneic stem cell transplant (alloSCT) recipients, but this observation has been challenged in developing countries such as Turkey, where Tb infection is more prevalent than in Europe and the US. In this retrospective study, we report on the incidence of Tb infections in 351 alloSCT recipients at 4 bone marrow transplantation units in Turkey over the last 10 years. The frequency of Tb in alloSCT recipients after allografting (5 of 351) was far greater than that in the general population (35.4 per 100,000). Of the 351 patients who underwent alloSCT, 77 who received isoniazid (INH) chemoprophylaxis for 6 months did not develop posttransplantation Tb. However, 5 of the remaining 274 patients who received no chemoprophylaxis developed Tb a median of 12 months (range, 10-47 months) after allografting. Antituberculosis therapy resulted in complete recovery in all cases. In 2 additional patients who were found to have active pulmonary Tb at the time of transplantation, alloSCT was delayed until the infections were treated. Infections of mycobacteria other than Mycobacterium tuberculosis were not observed. The number of patients who received and tolerated INH may not be sufficient for firm conclusions, but the data suggest that, in countries where Tb is prevalent, pre- and posttransplantation follow-up for Tb and the use of INH prophylaxis should be considered.