Loss of ADCC activity has only a partial effect on antitumor activity mediated by DI-Leu16-IL-2. Two different doses of native and enzymatically deglycosylated DI-Leu16-IL-2 were used to treat SCID mice beginning 7 days after injection of Daudi lymphoma cells. Treatments included PBS only (×; on days 7-11); rituximab (♦; 25 mg/kg on days 7, 9, and 11); medium-dose DI-Leu16-IL-2 (▪; 1 mg/kg on days 7-11); low-dose DI-Leu16-IL-2 (□; 0.25 mg/kg on days 7-11); medium-dose deglycosylated DI-Leu16-IL-2 (•; 1 mg/kg on days 7-11); and low-dose deglycosylated DI-Leu16-IL-2 (○; 0.25 mg/kg on days 7-11). Both high-dose groups of DI-Leu16-IL-2, with and without deglycosylation, were significantly different from all other groups (P < .005 or less), but were not significantly different from each other. The low-dose groups of these molecules were not significantly different from each other or from the rituximab group, but were significantly different from the PBS control (P < .0025 or less).