OUTLINE: This is a dose-escalation, multicenter study. Patients receive intraperitoneal interleukin-12 over 30 minutes once weekly for 4 weeks. Treatment repeats every 4 weeks for up to 6 courses in the absence of unacceptable toxicity or disease progression. Patients with stable or responsive disease may receive an additional 6 courses. Patients receive escalating doses of intraperitoneal interleukin-12 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose-limiting toxicity. Once the MTD is established, additional patients are accrued to receive interleukin-12 at the recommended dose.