We describe four patients who developed Guillain-Barré syndrome (GBS) following allogeneic bone marrow transplantation (BMT). All four patients had a febrile illness before developing GBS. Two patients had mild graft-versus-host disease but did not require immunosuppression. These patients add to the increasing number of BMT patients whose courses have been complicated by GBS and raise the possibility that BMT patients, especially those undergoing allogeneic BMT, may have a higher risk of developing GBS.