From May 1978 to September 1989 45 patients underwent 25 allogeneic and 21 autologous bone marrow transplantations (BMT) and 1 peripheral stem cell transplantation for the following indications: severe aplastic anemia (n = 4), hematological malignancies (n = 28), malignant solid tumours (n = 12) and sideroblastic anemia (n = 1). The first group of 20 patients was isolated in a conventional hospital room, while management of the aplastic phase in the second group of 25 patients was performed in a laminar air flow (LAF) unit. All patients received total decontamination. In a retrospective analysis the number of positive blood cultures during the neutropenic period was 85% in the first group, as compared with 40% in the second group, and the number of febrile episodes was 85% versus 64%, respectively. Despite the fact that the septic morbidity was lower in the LAF group, mortality during the neutropenic period (15% in group I versus 16% in group II) was unaffected and survival rate (45% in group I versus 36% in group II) did not improve. We conclude that LAF protection will only have a positive impact on survival rate if the incidence of non-infectious complications of BMT, such as organ toxicity or graft-versus-host disease, is likewise reduced.