In an effort to decrease the relapse rate following autologous bone marrow transplantation for non-Hodgkin's lymphoma, patients were given cyclosporine and interferon following autologous marrow transplantation. Forty patients with intermediate grade non-Hodgkin's lymphoma that was relapsed or refractory to standard chemotherapy underwent autologous marrow transplantation. The preparative regimen consisted of cyclophosphamide 6.8 g/m2, etoposide 1600 mg/m2, and carmustine 400 mg/m2 over 4 days followed by reinfusion of bone marrow. Intravenous cyclosporine was started on day -1 as a 16 mg/kg loading dose followed by 3.6 mg/kg/day for 28 days after transplant. Patients were begun on alpha-interferon (starting dose, 0.5 million units s.c. every other day) following platelet engraftment (median day 24 post-transplant) and continued on 1.5 million units s.c. daily for 2 years. Regimen-related toxicities resulted in four (10%) deaths. Twenty-one (53%) patients developed marked erythema of the palms, soles, and arms. Biopsies of the erythema were consistent with grade I GVHD. Patients who did not develop rashes were not biopsied. The erythema persisted for a median of 10 days and resolved in all cases without treatment. Visceral GVHD was not apparent. All patients have been followed for a median of 24 months (range 12-54 months). To date, only five patients (13%) have relapsed after bone marrow transplant. Multivariant analysis could not identify risk factors for relapse post-transplant. Disease-free survival of all patients is 77% (95% confidence interval, 67-93%). The results of this pilot study suggest that the administration of cyclosporine and interferon may decrease the relapse rate of relapsed/refractory non-Hodgkin's lymphoma following autologous bone marrow transplantation.