OUTLINE: This is a randomized, open label, multicenter study. Patients are stratified according to performance status (Karnofsky 60-80% vs 90-100%), age (less than 50 vs 50 and over), and time from initial diagnosis to recurrence (6 months or greater vs less than 6 months). Patients are randomized to one of two treatment arms. Arm I: Patients receive leflunomide (SU101) IV over 6 hours daily on days 1-4, again 4-8 days later, and weekly thereafter for a total of 4 loading dose infusions and six maintenance infusions in course 1. Patients receive 7 weekly maintenance infusions of SU101 in courses thereafter. Treatment repeats every 8 weeks. Arm II: Patients receive procarbazine orally once or twice daily for 4 weeks. Treatment is repeated every 8 weeks. All patients complete a health-related quality-of-life questionnaire every 8 weeks and at study withdrawal. Treatment courses continue up to a maximum of 1 year in the absence of unacceptable toxicity or disease progression. Patients are followed every 2 months, beginning 30 days after study completion.