OUTLINE: This is a dose-escalation, multicenter study. Patients are stratified according to concurrent use of enzyme-inducing anticonvulsant drugs (yes vs no drugs or modest-induction drugs). Patients receive SU5416 IV over 1 hour twice a week for 6 weeks. Treatment repeats every 6 weeks for 17 courses (approximately 2 years) in the absence of unacceptable toxicity or disease progression. Cohorts of 3-6 patients in each stratum receive escalating doses of SU5416 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity. Patients are followed every 3 months for 1 year, every 6 months for 4 years, and then annually for 5 years.