In a placebo controlled trial, the effect of the M1-antagonist telenzepine (3 mg in the morning) and of the dopamine antagonist domperidone (10 mg t.d.s.) was studied on bowel habits, on oro-caecal and on oro-anal transit time. The study was carried out on healthy subjects double-blind, multiple cross-over. The test periods were seven days each interrupted by wash-out periods of seven days. Stool weight, frequency and consistency as well as side-effects were recorded daily. The oro-anal transit time was estimated by evaluating the excretion of orally ingested radiopaque markers. The oro-caecal transit time was studied by means of a hydrogen breath test after a standard meal. The oro-caecal transit time was significantly prolonged during medication with telenzepine, both compared with placebo (p less than 0.05) and with domperidone (p less than 0.01). Bowel habits and the oro-anal transit time remained statistically unchanged during treatment with the active drugs. It is concluded that telenzepine has a dissociate effect on intestinal motility, delaying transit through the upper gastrointestinal tract without affecting the oro-anal transit time.