A national survey of tuberculosis after hematopoietic stem cell transplant (SCT) was undertaken to study incidence, clinical presentation and outcome. Twenty confirmed cases were found among 8,013 patients (eight in 5,147 autologous and 12 in 2,866 allogeneic SCT). The estimated incidence in cases/10(5) patients/year (95% CI) was 101 (56.5-145) for the whole group, 71.1 (21.8-120) in autologous and 135.6 (58.9-212) in allogeneic transplants. Compared with the general population, tuberculosis was more frequent after allogeneic (RR 2.95) but not after autologous SCT. Tuberculosis after SCT is a late infection (median 324 days post transplant), predominately affects the lungs (80% of the cases), appears to respond well to treatment but has a high mortality (25%) in allogeneic recipients. It can also complicate the post-transplant management as antituberculosis drugs frequently decrease the serum levels of cyclosporine causing an aggravation of GVHD. Graft-versus-host disease, corticosteroid treatment and total body irradiation appear to be associated with tuberculosis in allogeneic recipients. No obvious factors were associated with tuberculosis in autologous transplants. Finally, we found that the published literature on tuberculosis after solid and SCT has overestimated its incidence due to the direct translation of tuberculosis frequency into incidence.