This trial was carried out in Hospital Kuala Lumpur. Fifty-two patients who were scheduled to receive their first or subsequent courses of cancer chemotherapy with single dose cisplatinum containing chemotherapy regimens were evaluated. Thirty-four patients were given ondansetron in one group while 18 in the other group received metoclopramide with dexamethasone. The response to treatment was categorised as complete (0 emetic episode), major (1 or 2 emetic episodes), minor (3 to 5 emetic episodes) or failure (> 5 emetic episodes or rescue medication). Among the 52 patients, a complete or major control (0 to 2 emetic episodes) was achieved in 23/34 patients (68%) from the ondansetron group and in 3/18 patients (17%) from the metoclopramide with dexamethasone group (p < 0.002) on day 1. Similarly, the control of nausea was greater in the ondansetron group compared with the metoclopramide with dexamethasone group (p < 0.0009) on day 1. Two patients were excluded (dropped out) after day one from each of the two study groups due to excessive vomiting subsequent to cisplatinum therapy. From days 2 to 6, there was a trend in favour of ondansetron. Both treatments were well tolerated. The results of this trial show that in the prophylaxis of nausea and vomiting induced by cisplatinum containing chemotherapy, the efficacy of ondansetron is superior to that of a standard anti-emetic combination, metoclopramide with dexamethasone.