Ticlopidine is a potent inhibitor of platelet aggregation whose mechanism of action remains unknown. It might act through an increase of intraplatelet PGE1 and PGD2. Benign diarrhea is the most common side effect during ticlopidine treatment. We report four cases of severe chronic diarrhea with fecal incontinence in patients treated by ticlopidine. In two patients manometric recording of jejunal motility was performed. Abnormal motility patterns were observed in both cases: bursts of 3-11 propagated contractions occurring every 2 min and migrating at a rate of 0.6 cm/s, preceded and followed by a brief period of quiescence. Migrating motor complexes and a low percentage of time of quiescence were noted on both recordings. These disorders in intestinal motility may play a role in the pathogenesis of diarrhea observed with ticlopidine.