During the period of May 1986 through February 1991, nine allogeneic bone marrow transplants (BMT) on eight severe aplastic anemia (SAA) patients were performed at the Instituto Nacional de la Nutrición Salvador Zubirán in Mexico City. Mean age at BMT was 18 years (age interval 12-30); seven were men; all patients had a clinical history of multiple blood transfusions; six individuals were infected at the time of the transplant. The conditioning regimens were: cyclophosphamide (Cy) in three patients; Cy+ total nodal radiation in five; and total nodal radiation only in the second transplant of one patient. Graft versus host disease (GVHD) prophylaxis was attempted with methotrexate plus cyclosporin A (CsA) in six patients, methylprednisolone plus CsA in two, and prednisone + CsA in the patient retransplanted. All procedures were carried out under single reverse isolation without gut decontamination. Seven of the nine procedures grafted (two cases died on days +8 and +25 due to infection). In the surviving, the median time for reaching > 1.0 white blood cells x 10(9)/L was 22 days (time interval 11-31); > 0.5 neutrophils x 10(9)/L in 27 days (time interval 15-42) and the same lapse to reach > 50 platelets x 10(9)/L. Length of hospital stay was 42 days (time interval 15-61). Acute GVHD was seen in one of the seven patients surviving the period of bone marrow aplasia (14%). Of six long term survivors (including one patient with a second transplant) chronic GVHD was present in four (67%): chronic GVHD was fatal in one individual but was well controlled in three.(ABSTRACT TRUNCATED AT 250 WORDS)