This is the first report of a cardiac manifestation of a primary hyperoxaluria type II (PH II) with the hemodynamic characteristics of a severe restrictive cardiomyopathy. PH II is a rare inherited metabolic disease characterized by a deficiency of D-glycerate dehydrogenase, which has also glyoxylate reductase activity. This defect causes an accumulation of hydroxypyruvate the precursor of oxalate. The renal excretion of oxalate is impaired causing a deposition of oxalate mainly in the kidneys. To date, less than fifty cases have been reported. Systemic oxalosis in PH II is an occasional finding; thus far, myocardial oxalosis due to PH II has never been reported. Described is the case of a 41 year old male with renal failure and severe neuropathy of unknown cause, who underwent endomyocardial biopsy under the suspicion of cardiac amyloidosis. Echocardiography and cardiac catheterization showed a severe restrictive cardiomyopathy; endomyocardial biopsy established the diagnosis of oxalosis. Plasma oxalate levels were markedly increased, therefore a liver biopsy was performed. Immunoreactivity for D-glycerate dehydrogenase/ glyoxylate reductase was absent and activity of the enzyme was < 5% of normal. In summary, these findings established the diagnosis of a restrictive cardiomyopathy due to PH II.