The frontiers of behavior modification are changing. Five or six years ago, the central questions surrounding behavior modification focused on its application with individuals (e.g., Ullmann & Krasner, 1965). The primary questions then were whether behavior modification was as good as, or better than, traditional forms of treatment (Paul, 1966); whether behavior modification was really a placebo effect (Davison, 1968); whether behavior modification merely eliminated symptoms, leaving behind the basic neurosis (Baker, 1969); and similar issues. While it is not out intent to suggest that these issues have been resolved in any ultimate sense or that research in these areas has ceased, the issues have at least received wide exposure and are now part of the established concerns surrounding behavior modification. Although questions about behavior modification on the individual level are still to be resolved, a major new frontier of interest has opened up. This new frontier is centered around the application of behavior modification techniques to populations larger than one in natural settings (e.g., Ayllon & Azrin, 1968).