A case is reported of a 65 year old man who suffered myocardial ischemia resulting from extensive stenosis of the intramural coronary arteries secondary to systemic vascular involvement by primary amyloidosis. In the myocardium, there were multiple fibrotic foci scattered mainly in the subendocardial region of the ventricle. Intramural coronary arteries were stenotic or occlusive due to amyloid-induced luminal narrowing, but there was no significant stenosis of the epicardial coronary arteries. Quantitative analysis of amyloid deposits in the intramural coronary arteries demonstrated that occlusive arteries were predominant in the surrounding area of myocardial fibrosis, and the extent of coronary stenosis by amyloid deposition was significantly more severe than in hearts of the five control patients who had coronary amyloidosis without myocardial fibrosis. These results indicate that myocardial fibrosis originates from coronary ischemia due to vascular amyloid deposition. This is the first time that the relationship between myocardial lesions and coronary amyloid deposition has been elucidated using histopathologic quantitative analysis.