OUTLINE: This is a dose-deescalation study. Patients receive SU5416 IV over 1 hour twice weekly for 4 weeks. Treatment continues in the absence of disease progression or unacceptable toxicity. Cohorts of 6-12 patients receive deescalating doses of SU5416 until the maximum target-inhibiting dose (MTID) is determined. The MTID is defined as the dose at which patients experience no greater than grade 1 toxicity. Patients are followed every 3 months.