The social changes that have taken place in the past fifteen years have had a powerful effect on the life trajectories and social expectations of people in different age groups in Russia. For the most part there are two terms that are used to identify these groups: age cohort (or age group) and generation. But the use of these terms in sociological research has not been rigorous. The application stems from the tradition of the use of these terms in demography, influenced by journalistic writing, conventional thinking, and the personal tendencies of each individual sociologist. This article evaluates four waves of nationwide empirical surveys conducted in the Institute of Philosophy of the Russian Academy of Sciences (1990, 1994, 1998, and 2002). These surveys make it possible to trace the dynamic of the evolution of age cohorts during the years of societal transformations. (Contains 2 figures, 4 tables, and 2 notes.)