The antitumor activity of recombinant human interleukin-1 alpha (rHIL-1 alpha), recombinant human tumor necrosis factor, and recombinant murine interferon-beta (rIFN-beta) was augmented by concomitant administration of recombinant human interleukin-2 (rHIL-2) in the treatment of adenocarcinoma 755. Especially when a divided dose (two doses/day) of rHIL-1 alpha or rIFN-beta was combined with a divided dose of rHIL-2, the antitumor effect was markedly potentiated. However, only a marginal effect was seen by combination of rHIL-1 alpha and/or rIFN-beta and rHIL-2 against Lewis lung carcinoma, a tumor that is resistant to cytokines.