The role of molecular genetics in the pathophysiology of various diseases is becoming clearer and clearer. In the field of cardiovascular diseases, molecular genetic aspects have been shown to play a definite role in the aetiology of these diseases. Several molecular-genetic variations called polymorphisms, occur in the population. The genes encoding the different components of the reninangiotensin-aldosterone system (RAAS), an important system in the regulation of the function and structure of the heart and vascular wall, also display polymorphisms. For some of these polymorphisms associations with various cardiovascular and renal diseases have been described. At present, this is particularly clear for the relation between angiotensin-converting-enzyme (ACE) polymorphism and the incidence of atherosclerotic complications and diabetic nephropathy, and for the relation between so-called M235 T-variant of the angiotensinogen gene and hypertension. Future research will have to show where it is worthwhile to use these and other polymorphisms as a marker for genetic risk. In what way the different RAAS-polymorphisms relate to functional abnormalities is as yet unclear, as are the potential therapeutic implications.