The standard peritoneal equilibration test (PET) characterizes the peritoneal transport of fluid, creatinine and urea. However, the applicability of the standard PET may be limited in patients on cycling peritoneal dialysis due to the choice of 2- and 4-h sampling times which exceed the usual dwell time of most patients on cycling peritoneal dialysis. We have performed a modified PET on seven pediatric dialysis patients in an effort to optimize dwell time to achieve maximal clearance of solutes and fluid. When compared with the standard PET, values obtained for dialysate/plasma urea and dialysate/plasma creatinine with the modified PET are significantly different. This resulted in an increased estimated creatinine clearance in five of seven and increased estimated urea clearance in six of seven patients. The modified PET is a more appropriate method for evaluation of peritoneal clearances in children as well as older patients who may require cycling peritoneal dialysis.