Cohorts of 3-6 patients each receive escalating doses of intraperitoneal recombinant human interleukin-12 (rhIL-12) administered weekly for 9 weeks. If a patient tolerates rhIL-12 and shows evidence of objective response or stable disease, patient may receive up to 9 additional weeks of treatment. Treatment continues in the absence of unacceptable toxicity or disease progression. Dose escalation continues until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which no more than 1 of 6 patients experiences dose limiting toxicity.