Obesity is a growing clinical problem reaching epidemic proportions in developed and developing countries. It is associated with several comorbidities including cardiovascular diseases. There is strong evidence for the association of excess weight and established metabolic risk factors for coronary artery disease (CAD) such as hyperlipidemia, high blood pressure and type 2 diabetes. In addition, obesity may promote cardiovascular disease independent of these factors, possibly via hormones secreted by adipocytes, promotion of proinflammatory processes or other as yet unrecognized mechanisms. In this article the authors will outline the heredity of body weight and CAD/myocardial infarction and describe genetic factors involved in the etiology of these diseases. The methods commonly applied for the detection of such factors are described (e.g., animal models, linkage studies, association studies, etc.). These methods are discussed either in the paragraphs on obesity or on CAD; the described principles apply to both phenotypes.