Stone fragments remaining in the gallbladder are an important problem after ESWL. Cisapride (CIS) improves gallbladder contraction and hence we decided to investigate whether clearance of stone fragments after ESWL for radiolucent gallbladder stones can be increased by cisapride. Six to 15 months (median 12) after ESWL 48 patients with remaining gallstone fragments of less than 5 min in diameter were randomized either to Group A, who received cisapride 10 mg t.i.d. orally for 3 months in addition to oral litholysis (OLL) with ursodeoxycholic acid 500 mg/day and chenodeoxycholic acid 500 mg/day, or to Group B, who continued solely with OLL. All patients had started OLL within the fortnight-preceding ESWL. Gallbladder contractility, as measured by oral cholecystography with a fatty meal, was intact in all patients prior to ESWL. Maximal diameter and number of fragments were assessed by ultrasound (5 mHz) in different positions of the patient at the beginning of the study and after 3 months. Total clearance of fragments, which includes clearance of all sludge. occurred in only 3 patients, two of whom received only OLL. After 3 months the number of fragments decreased in 6 patients in Group A and in 7 patients in Group B. Three patients stopped taking cisapride before completion of the study, two because of diarrhoea, and one because of dysuria. All symptoms were readily reversible after discontinuing cisapride. In conclusion. cisapride combined with OLL does not enhance clearance of the gallbladder when fragments are still present one year after ESWL.