At the autopsy of a 25-year-old man who had died from combined morphine and cocaine intoxication, depositions of metallic mercury were incidentally found in the myocardium of the right ventricular septum and posterior wall. Deposits, toxicologically identified as mercury, were also found radiologically and histologically in the lungs. All these deposits were probably the result of intravenous injections of mercury many months previously, as is known to be done occasionally by addicts. Judging by the histological picture the greatest proportion of the mercury collected in the right ventricular cavity after injection, a smaller amount by embolization in the small pulmonary arteries. The mercury spheres which came to lie in the right ventricle then penetrated into the myocardium, moving outward and causing a chronic and partly transmural inflammatory response.