This paper attemps to trace the thread leading from the developmentalist schoool to present-day work on the life course. After a reminder of the early theories, it highlights three stages or landmarks. At the beginning of the seventies, formulation of the theory of age stratification was social gerontology's first major contribution to the understanding of post-industrial societies. Concomitantly, the methodological examination of age as an indicator or "independent variable" led to the clarification of concepts, the definition of various empirical research paths and the refinement of analytical techniques. Finally, during the eighties, under the impetus of mostly European research workers, the notions of life cycle and age stratification were reconsidered on the basis of a socio-historical approach. This article also encompasses the somewhat chaotic amount of qualitative researches, which pinpoints the importance of the symbolical reality (meaning) and often explores situations from a holistic point of view. In the last part, a discussion of the European and French-speaking contribution provides the opportunity for a comparison with the situation in North America and for a hypothesis on one consequence of the Durkheimian heritage on French sociology.