Cardiovascular beriberi is caused by thiamine deficiency and usually arises for one of two reasons: alcoholism or diet. Shoshin beriberi is a fulminant form of cardiac beriberi. We investigated the histopathological features of biopsied myocardial tissue samples from two patients with Shoshin beriberi (one patient with nonalcoholic beriberi and another patient with alcoholic beriberi). Interstitial fibrosis and a variation in size of the myocardial fibers were the main findings in the sample from these patients after thiamine treatment. These findings are persistent histopathological features in the myocardium of patients with Shoshin beriberi after thiamine treatment.