We report the case of a 23-year-old woman who developed severe myalgias in association with mild hepatitis B surface antigen-positive hepatitis. Muscle biopsy showed myriads of microvacuoles filled with neutral lipid. Prednisone therapy was associated with complete clearing of all clinical and laboratory abnormalities. Since muscle carnitine levels were normal before treatment, we conclude that infection with hepatitis virus may induce non-carnitine-deficient lipid storage myopathy in man.