Six cases of fatal pneumococcal sepsis are described, occurring in the post-allograft setting, between 3 and 39 months after transplantation. Five of the six patients were suffering from chronic graft-versus-host disease and were receiving immunosuppressive therapy. Most were receiving prophylactic antibiotic therapy. This represents approximately 2% of the allograft population treated during the study period who survived for > 3 months after transplant. Pneumococcal sepsis is thus still a significant cause of death after allogeneic BMT and approaches to minimise its occurrence are discussed.