To investigate how the use of T-cell-depleted marrow or a combination of cyclosporine and methotrexate to prevent graft-versus-host disease affect oral health and the ability to maintain adequate nutrition during the neutropenic phase after allogeneic bone marrow transplantation, 48 allogeneic bone marrow recipients were studied. From a group of adult leukemic marrow recipients of HLA identical sibling marrow, 23 patients were randomly chosen to receive T-cell-depleted marrow and 25 were selected to receive cyclosporine and four doses of methotrexate to prevent graft-versus-host disease. Before the transplantation, all patients were given all necessary dental treatment as well as oral hygiene and nutrition instructions. The oral mucosal and nutritional status in all patients (except one who died) were followed from 5 days before the procedure, during the neutropenic period after transplantation, and until discharge from the hospital. The number of oral lesions was similar in both groups. The subjective experience of orally related problems, such as pain from the oral cavity and number of days with total parenteral nutrition, was less in the T-cell-depleted recipients compared with those who received a graft-versus-host disease prophylaxis with cyclosporine and methotrexate (p less than 0.005). The oral cavity was considered to be the port of entry in four of six patients in the cyclosporine and methotrexate group who developed septicemia, compared with only one of six patients in the T-cell-depleted group with septicemia. The difference in the frequency of septicemia derived from the oral cavity did not, however, reach the significant level.(ABSTRACT TRUNCATED AT 250 WORDS)