High dose therapy followed by peripheral blood stem cell transplantation (PSCT) is a widely used therapy for relapsed or primary refractory patients with non-Hodgkin's lymphoma (NHL), however, relapses are frequent with this mode of treatment. IL-2 has shown efficacy in the treatment of patients with lymphoma. Post transplant immunotherapy with IL-2 given early after transplantation may be effective in eliminating tumor cells which survived the preparative regimen or were infused with the marrow or stem cells and thereby reduce relapses.