The antidiarrhoeic activity of the Euphorbia hirta whole plant was investigated. The lyophilized decoction demonstrated antidiarrhoeic activity in experimental models of diarrhoea induced by castor oil, arachidonic acid, and prostaglandin E2. It showed no activity when magnesium sulphate was used to provoke the diarrhoea. The lyophilized decoction delayed small intestinal transit when this was accelerated by castor oil but not in normal conditions. A flavonoid, quercitrin, with antidiarrhoeic activity was isolated from this crude drug.