A phase III, double-blind, placebo-controlled study was performed to examine the safety and efficacy of ramosetron in cancer patients with cisplatin-induced nausea/vomiting. Patients were divided into two groups: group R received 0.3 mg ramosetron intravenously and group P received placebo. Eighty-eight patients were enrolled, 44 in each group; 84 (43 in group R, 41 in group P) were included in the clinical efficacy analysis and 86 (44 in group R, 42 in group P) in the safety analysis. Ramosetron was significantly more clinically effective than placebo against nausea, vomiting and anorexia; 65.1% of patients in group R experienced no vomiting in the first 6 h of observation compared with 7.3% of those receiving placebo. No serious adverse reactions or significant differences in safety were observed between the groups. Based on these results, ramosetron injection is effective in the treatment of cisplatin-induced nausea/vomiting and its clinical usefulness is demonstrated here.