We evaluated the proliferation, cytolytic function, and phenotypic characteristics of anti-CD3 plus interleukin-2 (IL-2) stimulated peripheral blood mononuclear cells (PBMCs) from 44 patients with leukemia or non-Hodgkin's lymphoma (NHL) treated with multiagent chemotherapy or following bone marrow transplantation (BMT). BMT patients had decreased cell growth with only a 1.35 ± 0.25 (autologous BMT for acute lymphoblastic leukemia [ALL]), 1.24 ± 0.25 (autologous BMT for NHL), and 0.8 ± 0.1 (allogeneic BMT for leukemia) mean fold increase by day 5 of culture compared with controls (4.0 ± 0.4), P < .001. Anti-CD3 + IL-2 activated cells from patients with ALL and NHL who had received autologous BMT and cells from patients with leukemia who underwent allogeneic BMT were more effective in lysing the natural killer (NK) sensitive target, K562, and the NK-resistant target, Daudi, compared with controls. In contrast, cytolysis of K562 and Daudi by cultured PBMCs from patients with ALL and NHL receiving multi-agent chemotherapy was similar to that of controls. Cultures from BMT recipients had a significant increase in CD16+ (autologous ALL 5.7 ± 1.5%, P < .01; autologous NHL 12.4 ± 3.5%, P < .001; allogeneic 14.3 ± 2.9%, P < .001) and CD56+ cells (autologous ALL 27.6 ± 12.0%, P < .01; autologous NHL 39.3 ± 9.5%, P < .001; allogeneic 42.7 ± 7.4%, P < .001) compared with controls (CD16+ 2.5 ± 0.4%; CD56+ 6.9 ± 0.9%). Stimulation of PBMCs with anti-CD3 + IL-2 is effective in generating cells with high cytolytic function post-BMT.