Forty patients were allocated randomly to receive one of four premedications i.m.: placebo only, morphine 10 mg plus placebo, morphine 10 mg plus cisapride 10 mg and morphine 10 mg plus cisapride 4 mg. Gastric emptying after each premedication was assessed using the oral paracetamol absorption model. The morphine only group and the morphine and cisapride 4 mg group showed delayed gastric emptying when compared with the placebo group. Delay in gastric emptying in the morphine and cisapride 10 mg group was not demonstrated. It is concluded that cisapride 10 mg prevents the delay in gastric emptying associated with the administration of morphine.