This book is for social scientists concerned with the analysis of quantitative longitudinal data. It addresses difficult conceptual problems of measuring change with social science data, and the advantages of longitudinal data for constructing causal models of various kinds. A feature of this book is its emphasis on illustrating suggested approaches by careful analyses of actual research projects - the examples used come from a wide range of contexts within the social sciences and they are typical of the kinds of data collected by educationalists, social and developmental psychologists, social administrators, sociologists and political scientists.