This paper provides the teacher with a brief introduction to the principles of behavior modification. Major areas of concern deal with the history of behavior modification, implications for the concept of mental health, the teacher's role, the difference between behavior modification and other forms of control, reinforcement, the role of punishment in the behavior modification approach, informing the student of the "rules" of behavior modification and the ethical implications. Three case studies indicate the effects of behavior modification on the isolate behavior of a nursery school child, the control of a hyperactive child, and the effects of a token program. The summary indicates that although behavior modification cannot provide solutions for all problems, it can provide the teacher with an additional technique. A 26-item bibliography and a series of extracts from a report (March 1970) of the American Educational Research Association (AERA) meetings are included. (MJM)