Abdominal wall hernias have been increasingly recognized in patients on continuous ambulatory peritoneal dialysis (CAPD). They are also more frequent in children than in adults. The aim of this study was to determine the influence of intraperitoneal pressure (IPP) on the development of hernias in children on CAPD, and if there was a difference between IPP in children and adults. We studied 14 children aged 11.2 +/- 3.2 years, body weight 31.1 +/- 9.4 kg, who had undergone CAPD for 16.2 +/- 14.4 months. Also, 10 adults were studied, aged 48 +/- 18 years, body weight 62.4 +/- 13.9 kg, on the CAPD program for 35 +/- 27 months. The IPP was measured via a column of dialysate in the peritoneal dialysis line, immediately before the drainage of the peritoneal cavity. The pressure was measured with the patients in the supine position, at the level of the umbilical cicatrix with the zero point located on the mean axillary line. IPP was measured at inspiration and at expiration, and the mean of these two measurements was calculated. The children were divided in two groups: group 1 (n = 7) without hernias and group 2 (n = 7) with hernias (5 umbilical and 2 inguinal). The IPP of all children was 9.5 +/- 2.9 cm H2O. The IPP was 8.1 +/- 2.6 and 10.9 +/- 2.6 cm H2O in groups 1 and 2, respectively (P = 0.003). The instilled volume for test was similar in both groups. The IPP of the adults was 13.8 +/- 2.8 cm H2O, which was significantly greater than that of the children (P = 0.001). In conclusion, hernia is a common complication in children on CAPD and its prevalence is affected by IPP. Other associated factors may be the presence of anatomically weak sites in the abdominal wall of the children, since IPP is lower in children than in adults.