In the last decade, it has became apparent that the prescribed fill volume (IPV) in children on peritoneal dialysis (PD) should be expressed per body surface area (BSA in square meters) to avoid a false perception of peritoneal hyperpermeability as determined during a peritoneal equilibration test [PET, dialysate-to-plasma (D/P) ratio]. Nevertheless, the optimal IPV in terms of both tolerance and effectiveness remains under discussion. An individual approach to IPV prescription might balance the measurement of the intraperitoneal pressure, the use of the mass transfer coefficient despite the D/P ratio, and a determination of the effective peritoneal area available for exchanges. Considering these parameters, we usually found the individual optimal fill volume to be less than 1400 mL/m2.