The essential purpose of this paper is to illustrate the value of the Teacher Classroom Activity Profile (TCAP) in identifying and classifying teaching roles and in providing information which, if subjected to careful analysis, can lead to more effective approaches to the problem of role differentiation in the secondary school classroom. The author briefly describes the observational procedures used in a TCAP-based study of 1,097 secondary student teachers and reports the results (percent of classroom time devoted to various categories of behavior) in tabular form. He then presents and discusses the implications of seven hypotheses suggested by a preliminary analysis of the data (based on the seven categories of activity identified by the TCAP--i.e., management-nonlearning, management-learning, presentation, recitation, discussion, logical thinking, and attention to the thinking process). The analysis includes specific suggestions as to the ways in which teaching roles can be more effectively assigned and training programs more appropriately designed. (JS)