Polyethylene glycol (PEG-8000)-modified recombinant human interleukin-2 (PEG-rlL-2) is a ¢ytokine with prolonged circulatory half-life. In this paper, the antitumor effects of PEG-rlL-2 against mouse uterine cervical carcinoma (U₁₄) transplanted intraperitoncally or subcutaneously is reported. PEG-rlL-2 at different doses was administered intraperitoneally. The resuRs showed that PEG-rlL-2 (4500 IU, Lp., QDxS) prolonged survival time of mice bearing ascites tumor as compared to rIL-2 (P<0.01), but PEG-rlL-2 at lower doses was without therapeutic effect. In addition, compared to rIL-2, PEG-rIL-2 at different doses (1500-13500 112, s.c., QDx5) caused significant dose-dependent growth inhibition of solid tumor (P<0.01) when the treatment started at day 4 after subeutaneous inoculation of tumor.