Two 42-year-old male twins were referred to our hospital for coronary angiography within 3 months. Despite some gross similarities in the aspect of the coronary tree, the coronary dominance pattern was not the same in these twins, but coronary lesions involved almost the same sites. Genetically determined local factors, such as the rheologic profile in some sections of the coronary tree, or the susceptibility to lipid deposition in some spots, may be important in the development of atheromatous lesions in special sites.