Protein and energy requirements of children on automated peritoneal dialysis (APD) have still not been sufficiently well defined, although their adequacy is important to maintain a positive nitrogen (N) balance and prevent malnutrition. We carried out 42 studies to estimate N balance in 31 children over 3 years on APD for 19.8+/-15.7 months. Twenty metabolic studies were performed in patients dialysed for less than 1 year (7.2+/-3.3 months) and 22 in patients treated for more than 1 year (31.3+/-13.6 months). The mean estimated N balance of all metabolic studies was 57.5+/-62.8 mg/kg per day. In only 21 of 42 studies was N balance estimated to be over 50 mg/kg per day, which is considered adequate to meet N requirements for all metabolic needs and growth of uremic children. Estimated N balance correlated significantly with dietary protein intake (r=0.671, P=0.0001) and total energy intake (r=0.489, P=0.001). Using the equations of correlation, the values of dietary protein intake [=144% recommended dietary allowance (RDA)] and total energy intake (89% RDA) required to obtain an estimated N balance >50 mg/kg per day were calculated. Significantly lower estimated N balance values were obtained in the studies performed on patients on APD for over 1 year (36.09+/-54.02 mg/kg per day) than in patients treated for less than 1 year (81.11+/-64.70 mg/kg per day). In conclusion, based on the values of estimated N balance, we were able to establish adequate dietary protein and energy requirements for children on APD.