SummaryCardiovascular changes associated with Graves' disease are generally considered to be secondary to the increased levels Of thyroid hormone. We describe a case of Graves' disease in a 25‐year‐old man, who developed cardiomyopathy with severe heart failure. Pathological examination of the myocardial biopsies showed fibroblast infiltration and degenerative changes. After the cardiomyopathy subsided the patient developed a goitre and signs of hyperthyroidism, followed by Graves' ophthalmopathy, which was treated successfully with a combination of high‐dose corticosterolds and orbital radiotherapy. These findings suggested a common pathogenesis for the cardiomyopathy and ophthalmopathy, and prompted us to investigate the expression of TSH receptor (TSH‐R) in human heart. TSH‐R mRNA was identified in human heart using the reverse transcriptase‐polymerase chain reaction (RT‐PCR) and DNA sequencing. Taken together, these data suggest that autoimmunity against the TSH‐R mlght contribute to both the cardiomyopathy and ophthalmopathy in similar cases of