In the Rotterdam Study, prevalence and determinants of chronic diseases in the elderly (age > or = 55 years), were investigated in inhabitants of Ommoord, a suburb of Rotterdam. The study focused on cardiac diseases (myocardial infarction, angina pectoris, cardiovascular risk factors), glaucoma, macular degeneration, osteoporosis, osteoarthrosis and invalidity, dementia (Alzheimer's disease, vascular dementia, Parkinson's disease), epilepsy, cerebrovascular accident. The number of participants was 7983 (3105 men, 4878 women), a response of 78%. The participants were interviewed and were twice examined in an out-patient clinic. The results will be described in subsequent issues of this journal.