OBJECTIVES: I. Compare the antiemetic effect of ondansetron vs placebo in patients with advanced cancer who suffer from chronic nausea and emesis that is not due to antineoplastic therapy (i.e., chemotherapy, radiotherapy, immunotherapy, biologic therapy). II. Determine the toxicity of ondansetron in these patients. III. Evaluate the use of other concurrent antiemetics in these patients when treated with this regimen.