The antiemetic effect of prednisolone on nausea/vomiting was investigated in 67 patients with advanced prostatic cancer and a performance status of < or = 2. The study was a double-blind, placebo-controlled, randomized trial with a parallel group design. The objective was to compare the incidence and severity of nausea/vomiting between the two groups. Prednisolone or placebo was given twice daily for 3 weeks with the dose decreased during the third week from 15 mg/day to 10 mg for 3 days and finally to 5 mg/day during the last 4 days. EMP was given as two 140 mg capsules daily for 3 days at the beginning, then as four capsules for 4 days followed by six capsules for 21 days. Areas under curves (AUCs) for nausea and for nausea/vomiting scores were calculated based on the patient's diary notes: nausea (0-3), vomiting (0-6), nausea/vomiting (0-9). Control of emesis in terms of complete, moderate or poor control was registered. Pretreatment characteristics were evenly balanced. The results indicated that no statistical differences between the two groups of patients were present in AUCs for weeks 1-3 or weeks 1-4. We conclude that it was not possible to demonstrate a significant antiemetic efficacy of prednisolone. However, in all but one case the patients in the prednisolone group could be treated for at least 3 weeks without any major incidents of nausea/vomiting.