A 67-year old woman was emergently admitted because of fainting spells. Electrocardiography showed complete atrioventricular block, and echocardiography demonstrated reduced left ventricular systolic function. Decreased uptake was observed in multiple areas on thallium myocardial scintigraphy; however, coronary angiography showed no significant stenosis. Diffuse left ventricular hypokinesis and complete AV block strongly suggested cardiac sarcoidosis or amyloidosis, but a definitive diagnosis could not be established because histological evidence was lacking. Giant multinucleated cells were incidentally detected on gastric biopsy, and the diagnosis of sarcoidosis was made.