The effect of a new formulation of the gastric prokinetic agent cisapride on opioid-induced gastric stasis was investigated. Forty patients were randomly allocated to one of four therapies administered as premedication; group A, placebo suppositories only; group B, placebo suppositories and intramuscular morphine 10 mg; group C, rectal cisapride 30 mg and intramuscular morphine 10 mg and group D, rectal cisapride 60 mg and intramuscular morphine 10 mg. Gastric emptying was assessed from the small bowel absorption of paracetamol following oral absorption. The kinetics of the suppository formulation were determined from venous blood samples. Rectal cisapride in the two doses used did not prevent opioid-induced gastric stasis. This may reflect an inability of this formulation to produce adequate plasma concentrations.