To assess the outcome of infants on chronic peritoneal dialysis (PD), we retrospectively reviewed 21 patients who began PD prior to one year of age. Mean age at first dialysis was 56 +/- 56 days with mean weight of 3.6 +/- 1.6 kg. Seventeen infants were male and 17 were Caucasian. The most common primary renal diagnosis was renal hypoplasia/dysplasia, occurring in 7 infants. Mean time on PD was 10 +/- 10 months. Eleven infants had oliguria, and 10 infants had adequate urine output. All but 1 infant received tube feedings; mean caloric intake was 453 +/- 92 kJ/kg/day. Despite nutritional management, weight, height, and head circumference was at or above the fifth percentile in only 10, 4, and 5 infants, respectively. Nonrenal abnormalities were present in 12 of 21 infants with lung, heart, and central nervous system abnormalities occurring most often. Outcome included 7 receiving renal transplants, 1 who recovered renal function, 4 who continued on PD, and 9 who died. Seven infants with oliguria died, while only 2 infants with adequate urine output died. No infant with isolated renal disease died, while 9 of 12 patients with renal plus nonrenal abnormalities died. Thus mortality in infants less than one year of age on PD appears to be associated with the presence of oliguria and nonrenal abnormalities.