As a result of the theoretical risk of an excessive increase in intraperitoneal pressure (IPP) in association with peritoneal dialysis, reduction of instilled intraperitoneal dialysate volume (IPV) is often proposed in infants compared to adults; a further reduction is often noted in neonates compared to children. To better evaluate the significance of this risk, we have tested the relationship between the IPP (cm of water) and the IPV (mL/m2) in our population of children on peritoneal dialysis (n = 17) during the last three years. IPP was measured after a nocturnal dialysis session, during a morning study day, after sequential exchanges of ten minutes' dwell time each, with progressively increased instilled dialysate volumes from 600 to 1400 mL/m2. Mean IPP values were 8.2 +/- 3.8 cm for a mean IPV of 990 +/- 160 mL/m2 body surface area. These values are lower than the IPP values established for adults (13.4 +/- 3.1 cm), which were given for higher IPV values of 1585 +/- 235 mL/m2. The relationship between IPP and IPV was age-dependent. In neonates, stable IPP values (3.5 +/- 1.6 cm) were noted for IPV from 600 to 800 mL/m2; thereafter, increasing IPV led to an increase in IPP. In the range of 600 to 1200 mL/m2 IPV, no significant increment of mean IPP was noted in infants (4.8 +/- 2.6 cm) and in children (9.6 +/- 2.1 cm). However, increasing the dialysate volume over 1000 mL/m2 induced an overincrement of the individual IPP value in most cases, and the rise of IPP was substantial when IPV rose from 1200 to 1400 mL/m2.