The aim of this study was to investigate whether cisapride significantly increases corrected QT (QTc) intervals on resting 12-lead electrocardiograms (ECGs) in children on peritoneal dialysis. Medical records of children who were treated with chronic peritoneal dialysis and who had ECGs while off and on cisapride were obtained and reviewed. QTc on all 12-lead ECGs and past medical history were analyzed by two blinded pediatric cardiologists. A total of 79 ECGs (68 off/11 on cisapride) for 11 children on peritoneal dialysis were included. Of 11 children, 5 developed a prolongation of QTc, 2 of them beyond the normal range (453 and 478 ms). Mean data of QTc off versus on cisapride were 394+/-24 ms and 414+/-36 ms, respectively ( P=0.041). In 4 of the 5 children concomitant medications could be identified as factors to explain prolongation of the QT interval. No child had evidence of any arrhythmia or conduction defect on ECG. This retrospective study found mild but significant increases in QTc intervals with cisapride in children on chronic peritoneal dialysis, mostly due to concomitant medications.