There is a spectacular increase in life expectancy in nearly all countries worldwide. In this presentation I will discuss the counterside of this phenomenon: the increase in diseases in the elderly. I will address the possible causes of diseases of old age, using data from the Rotterdam Study, a prospective follow-up study of 15 000 persons of 45 years or over that is, being conducted in a district of the city of Rotterdam, The Netherlands, since 1990. I will argue that ageing, as applied to the individual rather than the population, is an empty concept. In my presentation a particular focus will be on the possible genetic causes of disease in the elderly, and on possible gene-environment interaction. I will discuss the recent avalanche of genes found through genome-wide association studies, and the application of these findings in the study of disease etiology, prediction, treatment and prevention.