OBJECTIVES: I. Determine the maximum tolerated dose of combretastatin A4 phosphate when administered at single doses every 21 days in patients with advanced solid tumors. II. Determine both the toxicity and dose limiting toxicity of this regimen in these patients. III. Determine the plasma and urine pharmacokinetics of combretastatin A4 and combretastatin A4 phosphate. IV. Gather preliminary data regarding possible antitumor effects in those patients with measurable disease.