Chick bioassay of angiotoxicity of 7-ketochoiesterol was performed in this study. Dietary cholesterol feeding induced more lipid deposition of connective tissue cells than neighboring smooth muscle cells of ascending and thoracic aorta. Abdominal aorta had little response to cholesterol. 7-ketocholesterol supplementation to diets with or without cholesterol resulted in frequent dead and dying smooth muscle cells especially in abdominal aorta. These data support the hypothesis that oxigenative sterol is more potent angiotoxin than cholesterol itself.