In a long follow-up period of 23 years about 600 teenagers were observed till their young adult age in order to investigate the longitudinal relationship between health and lifestyles considering physical activity, diet, smoking and alcohol consumption. Longitudinal studies with a follow-up lasting for a quarter of a century are very rare and the Amsterdam Growth and Health Longitudinal Study (AGAHLS) is indeed unique among them. The focus is multidisciplinary and involves both physical and psychological determinants in relation to a wide range of health outcomes. The multiple measurements were carefully standardized in nine waves of data collection, thus producing a high-quality data set, which has been analyzed by the application of advanced statistical techniques. The monograph provides not only an overview of 23 years of follow-up, it also summarizes over 200 scientific publications and 10 PhD theses. This publication is especially recommended to investigators planning longitudinal research, to health workers, and to authorities who like to implement health promotional activities in their community.