Emetic responses to cisplatin and participation of vagal innervation in emesis were studied in suncus. Intraperitoneal and intravenous administration of cisplatin caused dose-dependent emesis. ED50 values, latencies and frequencies were not significantly different between the two administrations. Cis-diaqodiammineplatinum (DAP), an active metabolite of cisplatin, also induced emesis, but with significantly shorter latency. Vagotomy completely abolished both types of vomiting. These results suggest that cisplatin is metabolized to DAP that subsequently causes emesis through stimulation of the vagus afferent.