Mepirizole (60 and 200 mg/kg, s. c.) and cysteamine (100 and 300 mg/kg, s. c.) markedly inhibited gastric motility in fasted rats. The inhibition caused with the low dose (non-ulcerogenic) of each agent reverted to control levels within 6h. With high doses (ulcerogenic), however, the inhibition persisted for more than 9 h, and returned to control levels 12 h later. Gastric emptying of liquids was significantly delayed with ulcerogenic and non-ulcerogenic doses of the agents. Delayed emptying (gastric contents) persisted for 12 h with ulcerogenic doses, The pathogenetic relevance of this prolonged inhibition of gastric motility and emptying to ulcerogenecity was considered.