We report a case of a patient complaining of severe chest pain which required a differential diagnosis between cardiovascular disease and sternocostoclavicular hyperostosis. The patient was a 61-year old male who began experiencing pain across both scapulas at the end of September, 1990. He was admitted to our hospital when the pain extended to the back and anterior chest areas. Examination on admission revealed inflammation with a white blood cell count at 11,800/mm3, an erythrocyte sedimentation rate of 136 mm/hr, and CRP at 14.2 mg/dl. Angina pectoris was suspected based on findings from coronary arteriography which showed 60% stenosis at Seg 6. A Ga-scintigram conducted to determine the cause of the chest pain revealed accumulations in the upper mediastinum. CT and MRI both showed hyperostosis of the sternum, and bone scintigram confirmed marked accumulations in the same area. Palmoplantar pustulosis (PPP) was also clearly noted on the palms and soles of the feet. Sternocostoclavicular hyperostosis was diagnosed based on these findings. Sternocostoclavicular hyperostosis was suspected in this case based on the clinical findings, inflammatory state, and accumulations revealed by bone scintigraphy. However, the diagnosis could have been more conclusive if non-suppurative hyperosteostic osteomyelitis were observed by bone biopsy. A differential diagnosis for unknown sources of chest pain should be considered in cases such as this.