Plasma carnitine and the effect of oral carnitine supplementation on serum triglycerides was studied in 12 pediatric patients receiving continuous ambulatory peritoneal dialysis (CAPD). Baseline evaluation of all patients included plasma carnitine and serum triglyceride values. Following randomization into two groups, only group 2 patients received oral L-carnitine supplementation, 100 mg/kg/day, for 2 months. The initial laboratory evaluation was repeated at the conclusion of the study. Plasma carnitine values were also determined from a control population. Mean baseline plasma carnitine concentrations of group 1 (39.8 +/- 8.0 nmol/ml) and group 2 (45.2 +/- 10.3 nmol/ml) patients were not significantly different from each other or from the control population. Serum triglyceride values were elevated in both groups (group 1 - 206.5 +/- 100.0 mg/dl; group 2 - 279.3 +/- 74.5 mg/dl). After 2 months, the mean plasma carnitine concentration of group 2 patients increased to 147.7 +/- 84.1 nmol/ml, significantly greater than the value of group 1, 32.8 +/- 8.0 nmol/ml (p less than 0.004). However, no significant change in the serum triglyceride level was noted in either group. We conclude that the plasma carnitine status of pediatric patients receiving CAPD is normal and that oral carnitine supplementation does not lead to the resolution of hypertriglyceridemia.