OUTLINE: This is an open label, nonrandomized, multicenter study. Patients are stratified into two categories of prior failed treatments (first relapse after autologous bone marrow or peripheral blood stem cell transplantation vs first or subsequent relapse either refractory to or not eligible for further conventional treatment). Interleukin-2 (IL-2) is administered as a continuous intravenous infusion on 5 consecutive days at daily escalating doses for the first cycle. When the individual maximum tolerated dose (MTD) has been determined, 3 more cycles are given at the MTD. There are 3 days of rest between each treatment cycle. After the induction phase, maintenance cycles of IL-2 are administered starting 4 weeks after the last induction treatment. Maintenance cycles of IL-2 are administered subcutaneously on 5 consecutive days every 4 weeks for 2 years, and subsequently every other month for a maximum of 3 years. Treatment continues until disease progression or unacceptable toxicity for a maximum of 5 years. Patients are followed every 4 weeks during the first 2 years, then every 8 weeks during the next 3 years or until documented progression, and then every 3 months until death.