A comparative clinical trial of tropisetron capsule was conducted in three dose groups to investigate its optimal dose on nausea and vomiting induced by anti-cancer drugs, including cisplatin. The doses were randomized by the central registration office. In the assessment of clinical efficacy, cases rated as "effective" or better accounted for 61.5% of the 2.5 mg group (16/26), 80.8% of the 5.0mg group (21/26) and 80.0% of the 10mg group (24/30), respectively; the ratings for the 5mg and 10mg groups were almost equivalent, which was higher than that for the 2.5mg group. Adverse events observed were fever, diarrhea, drowsiness, headache and/or facial erythema in 4 out of 97 cases. Abnormal laboratory findings noted were 6 cases of increased GOT, GPT, LDH, total bilirubin and/or creatinine, but none of these was serious or clinically problematic in particular. On the basis of the above results, the optimal dose of Tropisetron (capsule) is considered to be 5mg once daily.