The rapid growth of behavior therapy over the past 20 years has been well doc umented. Yet the geometric expansion of the field has been so great that it deserves to be recounted. We all received our graduate training in the mid to late 1960s. Courses in behavior therapy were then a rarity. Behavioral training was based more on informal tutorials than on systematic programs of study. The behavioral literature was so circumscribed that it could be easily mastered in a few months of study. A mere half-dozen books (by Wolpe, Lazarus, Eysenck, Ullmann, and Krasner) more-or-Iess comprised the behavioral library in the mid- 1960s. Semirial works by Ayllon and Azrin, Bandura, Franks, and Kanfer in 1968 and 1969 made it only slightly more difficult to survey the field. Keeping abreast of new developments was not very difficult, as Behaviour Research and Therapy and the Journal of Applied Behavior Analysis were the only regular outlets for behavioral articles until the end of the decade, when Behavior Therapy and Be havior Therapy and Experimental Psychiatry first appeared. We are too young to be maudlin, but "Oh for the good old days!" One of us did a quick survey of his bookshelves and stopped counting books with behavior or behavioral in the titles when he reached 100. There were at least half again as many behavioral books without those words in the title.