Increased plasma oxalic acid concentrations have been found in patients with chronic renal failure. Secondary oxalosis in patients on chronic hemodialysis is caused by impaired renal excretion and inadequate removal of oxalic acid during hemodialysis. 1,2 The oral or intravenous administration of ascorbic acid aggravates the elevated plasma oxalic acid in patients on hemodialysis. 3 As a consequence of increased plasma oxalic acid levels, calcium oxalate deposits have been found in myocardium and other organs. 4 We report a patient treated with chronic hemodialysis with diffuse calcinosis in the myocardium at autopsy. In this patient, who had undergone parathyroidectomy, a high intake of ascorbic acid led to increased oxalic acid synthesis and calcium deposits in many tissues.