The first essay described Cressey, the man, and analyzes his ideas and commitment to criminological research. The second essay explores Cressey's position on the uses of criminological knowledge and the rehabilitation of offenders. The next essay discusses the development of the differential association theory, reviews Kornhauser's critique, and proposes future direction for theoretical and empirical research. The fourth essay explores how differential social organization may be related to differential associations. Also, it assesses whether the effects of differential association variables and others from competing theories vary according to the social-class characteristics of the delinquents' social areas. The fifth essay reviews the sociology of the prison and Cressey's influence in this field. The final essay presents an evaluation of the contributions of Donald Cressey to the study of organized crime. Notes and references.