OUTLINE: This is a dose-escalation study. Patients receive interleukin-12 (IL-12) IV as a single test dose followed by 2 weeks of rest. Patients then receive IL-12 IV daily for 5 days followed by 16 days of rest for up to 6 courses. Cohorts of 3-5 patients receive escalating doses of IL-12 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 5 patients experience dose-limiting toxicity. Patients are followed until death.