To achieve more adequate dialysis in a shorter treatment time, seven children, characterized as high/high average (H/HA, 5 patients) and low/low average (L/LA, 2 patients) transporters according to the peritoneal equilibration test, were treated with tidal peritoneal dialysis (TPD) for 13.7 +/- 5.7 months, after being treated with nightly intermittent peritoneal dialysis (NIPD) for a similar period. We determined the TPD prescription necessary to provide improved clearances compared with NIPD within the same or less treatment time. Dialysis flow rate was significantly higher in TPD than NIPD, due to a reduction of dwell time and an increase in the number of exchanges. Peritoneal and total clearances of urea and creatinine were higher, whereas serum creatinine and urea nitrogen levels were lower and treatment duration shorter during TPD than NIPD, notwithstanding a decrease of residual renal function. Moreover, a mean time-averaged blood urea nitrogen level as low as 48.5 +/- 11.6 mg/dl was achieved during TPD. The improvement was more significant in H/HA than in L/LA patients.