The text introduces basic concepts of cohort analysis – age, period and birth cohorts. The author shows the role of birth cohorts in explanation of social processes and deals with a cohort replacement as a matter of social change. From the methodology point of view the author presents the standard cohort table, introduces an identification problem and shows two ways how to solve it using the data on birth rates in the Czech Republic between 1948 and 2007. The first solution is presented for population data, the second one is presented for microdata in the form of a series of repeated cross-section sample surveys. The results of both analyses show, that identification of age, period and cohort effects is important for interpretation trends in birth rates in the Czech Republic between 1948 and 2007., Tomáš Katrňák., and Obsahuje bibliografii a bibliografické odkazy