The goal of this dissertation is to enhance our understanding of the micro and macro level determinants of retirement timing in contemporary Western Europe. This objective is pursued by means of a statistical analysis of large-scale comparable survey data. In short, three points of emphasis characterize this study in comparison with previous research on the topic: 1) the focus on social stratification in terms of gender and class differentials; 2) the central attention paid to social norms of aging; and 3) the joint consideration of individual and country level mechanisms in explaining retirement timing. The review of the previous literature in the second chapter demonstrates that the currently available theoretical approaches by themselves are inappropriate for explaining social variability in retirement timing. Building on the life course paradigm and social class theory, I consequently outline a novel analytical framework for the study of differential retirement behavior.  It can be characterized as a choice-within-constraints approach (chapter 3), which essentially focuses on differences between older workers in age norms and late-career opportunity structures, paying special attention on class and gender disparities.  In the fourth chapter, I gather empirical evidence on international and individual differences in retirement age norms in Western Europe on the basis of data from the European Social Survey (ESS). Subsequently, I turn to examining actual retirement behavior in the fifth chapter. Using data from the Survey of Health, Ageing and Retirement in Europe (SHARE) a series of event-history models is used to scrutinize the determining factors of retirement timing at the country and individual level variation. In chapters 6 and 7, two case studies on Germany and Spain examine the impact of pension legislation on social stratification in retirement in a detailed manner. The two country studies are based on ad-hoc module on the transition from work into retirement, which has been implemented in the respective national labor force surveys (Encuesta de la Población Activa (EPA) and Mikrozensus) of 2006.