Recombinant interleukin-2 (IL-2) has been demonstated as an antineoplastic agent in mice and human, and the route of administration is important to IL-2-induced therapeutic responses. Therefore, the current experiment was undertaken to clarify the effect of IL-2 administration route on antitumor response against subcutaneous Meth-A tumor in mice. At the beginning of each experiment, normal BALB/c mice were injected subcutaneously with $5{ imes}10^6$ Meth-A tumor cells. Beginning on day 7, experimental groups were treated with a 5-day course of IL-2 (intraperitoneal or subcutaneous injection of 30, 000 IU every 12 hours for 5 days). The result of this experiment revealed that Meth-A tumor grew progressively in control mice. Intraperitoneal IL-2 treatment decreased significantly tumor growth and prolonged survival, compared with control mice. Subcutaneous IL-2 treatment decreased significantly tumor growth until day 11 and tumor cells, grew progressively thereafter, but mice in this group survived longer than control mice.