While success of autologous bone marrow transplantation (BMT) for malignancies largely depends on the cytotoxicity of the ablative regimen, achievement of relapse-free survival after allogeneic BMT is thought to be enhanced by immunologic effects. We therefore investigated in vivo and in vitro production of interferon-gamma (IFN-gamma), soluble interleukin-2 (IL-2) receptor alpha-chain (sCD25), tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients before and during various time periods up to 2 years after autologous and allogeneic BMT. Cytokine levels were assessed in patient plasma and in supernatants of patient-derived peripheral blood mononuclear cells (PBMNC) cultured for 3 days in the presence of T cell-specific stimulation via CD3 plus IL-2. Our studies show that IFN-gamma plasma levels are decreased in autologous graft recipients before and during the first 30 days posttransplant. In allogeneic graft recipients, IFN-gamma plasma levels are also decreased during the first 30 days posttransplant, but otherwise are comparable to normal control (NC) values. In vitro stimulated PBMNC from autologous graft recipients also exhibit an IFN-gamma production defect before and during the first 30 days posttransplant. In contrast, before and up to 30 days after allogeneic BMT, stimulated IFN-gamma production is comparable to NC values but then gradually decreases, reaching its trough levels at between 61 and 180 days post-BMT. The IFN-gamma production defects in both patient groups seem to be specific, as sCD25, TNF-alpha, and GM-CSF production in stimulated PBMNC is normal or even enhanced at any time after autologous or allogeneic BMT. Deficient IFN-gamma production in patient-derived PBMNC does not correlate with variation in monocyte, T cell, or natural killer (NK) cell numbers during the posttransplantation course.