Teacher professionalization—the movement to upgrade the status, training, and working conditions of teachers—has received a great deal of interest in recent years. This report is concerned with the effects of teacher professionalization on elementary and secondary teachers in the United States. The analysis assesses the effects of teacher professionalization by examining the relationships between a selected set of characteristics, traditionally associated with professions and professionals, and one of the most important aspects of the quality and performance of teachers: their commitment to their teaching careers.