The effect on the intestinal passage of 3 X 1 mg difenoxin hydrochloride (Lyspafen) was tested in a randomised double-blind study; the trial included 10 healthy volunteers and lasted one week. The time until elimination of both the first and twentieth of the total of 30 applied radiopaque stool markers was measured. The total weekly weight and number of stools served as further test criteria. The treatment with difenoxin and that without placebo were compared with the standard treatment using placebo. The extensive statistical evaluation failed to reveal significant differences in the criteria observed.