This article, the introduction to a collection of six related articles, describes the general rationale and design of the Berlin Aging Study (BASE). The distinguishing features of BASE are: (1) a special focus on the very old (70-105 years), (2) broad inter-disciplinarity (medicine, psychiatry, psychology, sociology and economics), and (3) sample heterogeneity achieved by local (West Berlin) representativeness. In addition to discipline-specific topics, four theoretical orientations guide the study: (1) differential ageing, (2) continuity versus discontinuity of ageing, (3) range and limits of plasticity and reserve capacity, and (4) ageing as an inter-disciplinary and systemic phenomenon. To provide a foundation and framework for the remaining articles, this paper outlines the protocols, designs, and measurement procedures of fourteen data collection sessions. In addition, information is given on the samples used for empirical analysis. Two samples from the first wave of the Berlin Aging Study are addressed in this collection of articles. The first (N = 360), uses data from the BASE Intake Assessment Protocol (Session 1). The second (N = 156), employs data from the entire 14-session full protocol of BASE. Selectivity analyses involving 22 comparison variables are reported in this paper and demonstrate that, with the exception of In-month mortality, these two samples displayed the intended sample heterogeneity. Those results suggest that data from BASE hold high generalizability.
