Treatment will consist of four courses of IL-2 and IL-12. On days one and nine of each course, patients will receive three doses (one every 8 hours) of IL-2 intravenously (through a vein). On days two, four, six, 10, 12 and 14, they will receive IL-12 intravenously. This will be followed by a recovery period from days 15 through 35. This regimen will be repeated for another three cycles; patients who show benefit without severe side effects may continue for additional cycles. Treatment for the first cycle will be administered in the hospital. If the drugs are well tolerated, additional therapy may be given on an outpatient basis.