SUMMARYMotor changes could be involved in the pathogenesis of diarrhoea that complicates the treatment of ulcer disease by prostaglandins. Our aim was to assess the effect of enprostil, a synthetic analogue of PGE2, on duodeno‐jejunal motility. During this randomized double‐blind crossover study, two manometric recordings, each lasting 20 h (12.00‐08.00 hours), were carried out during dosing with 35 μg enprostil b.d. or placebo (eight volunteers: part 1), or during dosing with 35 or 70 μg enprostil b.d. (nine volunteers: part 2). Subjects were only allowed a standard dinner at 18.00 hours.During fasting, in part 1, the number of phase 3 activity patterns (PIIIs) was higher with enprostil than with placebo (P<0.01), without any difference in their characteristics; the overall duration of phase 1 activity was longer with enprostil than with placebo (P<0.01). In part 2, during fasting the number and characteristics of the PIIIs were not different, but there was a dose‐related increase in PI, and decrease in PII activity. Fed motor patterns did not differ between the two doses of