Lipid profile analyses were performed on serum samples from six children (ages 4-17 years) who had previously been subjected to orthotopic liver transplantation. All six patients were receiving prednisone and cyclosporine and four were additionally receiving azathioprine. Marked elevations in serum triglycerides (greater than 95%) were seen in 3/6 patients, while a notable decrease (less than 5%) in HDL-cholesterol was noted in 4/6 patients. Total serum cholesterol was normal in all patients. Postheparin lipase activity determined in the serum of one patient revealed a significant decrease compared with control values. These observations suggest the need for studying large numbers of liver transplant recipients to determine the prevalence of lipid abnormalities and to consider their potential contribution to the development of premature atherosclerotic disease.