OUTLINE: This is a randomized, parallel, open label, multicenter study. Part I: Patients receive one of three doses of interleukin-2 (IL-2) subcutaneously beginning 20 to 40 days following autologous stem cell reinfusion. IL-2 is administered for 5 consecutive days every 14 days for up to 3 months, for a total of 6 courses. Cohorts of 5 patients are entered at each dose level of IL-2 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which 3 or more patients experience dose limiting toxicity. Part II: Additional patients receive IL-2 at the dose level below the MTD. These patients are stratified according to prior therapy (melphalan plus megatherapy vs total body irradiation or meta-iodobenzylguanidine scan plus melphalan vs busulfan containing regimens). Patients are followed at 1 week.