The peritoneal equilibration test (PET) is routinely performed in adults treated with chronic peritoneal dialysis to assess the peritoneal transport rate and to optimize treatment prescription. Only a few and not well-standardized studies on the PET have been reported in children. Twenty-six PET's were performed in 16 children, mean age 10.9 +/- 4.9 years, mean body weight (BW) 26.8 +/- 11.9 kg, treated with nightly intermittent peritoneal dialysis (NIPD). The PET was performed according to Twardowski. Forty mL/kg BW of 2.27% glucose solution were infused at a rate of 10 mL/kg BW every 2 minutes. In the simplified test, dialysate samples were taken at dwell times 0, 2 and 4 hours for glucose and creatinine. A blood sample was taken after a 2-hour dwell time for the same parameters. The standard PET (8 patients) consisted of dialysate samples at 0, 15, 30, 60, 120, and 240 minutes and blood samples at 0 and 240 minutes. Mean D/P ratio for corrected creatinine and D/D0 ratio for glucose at 2 hours were 51.6 +/- 11.6 and 50.4 +/- 9, respectively; at 4 hours 69.6 +/- 12 and 34.4 +/- 9.8, respectively. There was good correlation between D/P creatinine and D/D0 glucose at 4 hours (p < 0.0001). Patients were classified as high (3 cases), high-average (5), low-average (6), and low (2) transporters. A statistically significant difference was found between the curves obtained by the simplified PET and those of the standard PET in the first hour (r = 0.66; p < 0.05). In conclusion, the PET, modified for use in children, gave reliable and reproducible results.(ABSTRACT TRUNCATED AT 250 WORDS)