Support has recently been voiced for the genetic hypothesis of Alzheimer's disease; frequently at the expense of considerations of environmental factors. In the adult, genetic diseases rarely exist without modification by environment forces. Atherosclerosis leading to myocardial infarction may provide a useful model to consider genetic and environmental factors in Alzheimer's disease. Familial hypercholesterolemia produces a premature inherited form of myocardial infarction, whereas, atherosclerosis with myocardial infarction, seen in advanced age, relates more closely to environmental factors such as smoking, diet, etc.