Coronary artery aneurysms are rare and are diagnosed almost exclusively by angiography. Apart from a particular form of coronary artery sclerosis congenital malformations and various inflammatory diseases are to be considered aetiologically. Different opinions exist as to the clinical relevance and prognosis as well as to the necessary treatment of coronary artery aneurysms. Over the last 7 years we have observed 10 patients with in part grotesque dilatations of the coronary arteries. Based on the history and the other findings coronary sclerosis or/and congenital malformations had to be assumed. Follow-up of up to 6 years permits not an unfavourable prognosis which is more determined by the accompanying stenosing coronary sclerosis. Due to the danger of thromboses prophylaxis with platelet aggregation inhibitors is recommended. In dilated vascular disorders only surgery should be considered as the exception.