Persistent abnormalities of liver function tests occur in approximately 15% of home parenteral nutrition (HPN) patients and are associated with steatosis, steatohepatitis, and, rarely, fibrosis or cirrhosis. Approximately one-third of patients with gut failure on long-term HPN have low total and free plasma carnitine concentrations, and it has been suggested that a deficiency of L-carnitine may be responsible for the steatosis and steatohepatitis in HPN patients. To determine whether administration of L-carnitine is capable of reversing steatosis in HPN patients, 4 adult women on HPN for a mean of 53 mo (range 21-80 mo) were studied before and after 1 mo of intravenous L-carnitine supplementation (1 g/day). All patients had abnormalities in standard liver function tests and low total and free plasma carnitine values. The mean total and free plasma carnitine concentrations and the mean total hepatic carnitine concentration were reduced before supplementation and rose to normal values after treatment (27.4 +/- 2.3 to 35.5 +/- 3.1 nmol/ml, 19.4 +/- 2.8 to 25.7 +/- 2.5 nmol/ml, and 3.5 +/- 0.65 to 6.5 +/- 1.2 nmol/mg of noncollagen protein, respectively). However, there were no significant changes in mean serum aspartate aminotransferase and alkaline phosphatase levels (65 +/- 21 vs. 54 +/- 12 IU and 429 +/- 220 vs. 472 +/- 224 IU, respectively), plasma free fatty acids, plasma triglycerides, hepatic free fatty acid and triglyceride concentrations, or the grade of hepatic steatosis on light microscopy. These results suggest that carnitine deficiency is not a major cause of steatosis and steatohepatitis in patients receiving HPN.