[en] Background and purpose: Nausea and vomiting are frequent side effects during adjuvant abdominal radiotherapy in seminoma stage I patients. This study evaluates the efficacy and side effects of prophylactically administered tropisetron in comparison to metoclopramide. Materials and methods: Twenty-three seminona stage I patients who were to undergo adjuvant abdominal radiotherapy (30 Gy) were included in a prospective, randomised, open study. The patients were allocated to receive adjuvant daily tropisetron 5 mg p.o. (TROP group) (11 patients) or metoclopramide 30 mg p.o. (MET group) (12 patients), allowing an eventual dose increase to 60 mg. Evaluation was based on diary cards filled in by the patients during the treatment period. Nausea, vomiting, abdominal pain and bowel motions were assessed. Results: Nausea was significantly lower in the TROP group as compared with the MET group (median: 0.14 vs. 1.32; P = 0.03). Thirty percent of all patients experienced vomiting. In the TROP group one patient had a mean number of emetic events > 0 as compared with 6 patients in the MET group (P = 0.07). Two patients in the TROP group and one in the MET group discontinued therapy due to lacking control of emesis. In two further patients the doubling of the metoclopramide resulted in acceptable control of nausea/vomiting. Both drugs were generally well tolerated. Conclusion: Seminoma stage I patients on tropisetron experienced less nausea and vomiting during abdominal radiotherapy than patients receiving metoclopramide. The costs of the former drug may, however, not justify its use as first choice anti-emetic since few patients in either group experienced severe nausea