A 7-year-old girl developed recurrent episodes of hepatic and cerebral dysfunction which mimicked those in Reye syndrome (RS). Because of mild muscle weakness, she had repeated muscle biopsies which showed markedly increased amounts of lipid droplets, predominantly in type 1 fibers. Liver histological examination showed widespread hepatocellular steatosis. However, diffuse microvesicular fat, seen in RS, was not found in the cytoplasm. The concentrations of free- and acylcarnitine in serum and muscle were within normal ranges. Normal ketogenesis was induced by fasting. Based on the clinical, laboratory, and histopathological findings, our patient was initially thought to have systemic carnitine deficiency. However, the serum and muscle carnitine levels were within normal limits. Although the primary metabolic defect has yet to be elucidated, the present study indicates that lipid storage myopathy in the absence of carnitine deficiency can be complicated with RS-like episodes.