It is particularly gratifying to prepare a second edition of a book, because there is the necessary impli cation that the first edition was well received. Moreover, now an opportunity is provided to correct the problems or limitations that existed in the first edition as well as to address recent developments in the field. Thus, we are grateful to our friends, colleagues, and students, as well as to the reviewers who have expressed their approval of the first edition and who have given us valuable input on how the revision could best be structured. Perhaps the first thing that the reader will notice about the second edition is that it is more extensive than the first. The volume currently has 41 chapters, in contrast to the 31 chapters that comprised the earlier version. Chapters 3, 9, 29, and 30 of the first edition either have been dropped or were combined, whereas 14 new chapters have been added. In effect, we are gratified in being able to reflect the continued growth of behavior therapy in the 1980s. Behavior therapists have addressed an ever-increasing number of disorders and behavioral dysfunctions in an increasing range of populations. The most notable advances are taking place in such areas as cognitive approaches, geriatrics, and behavioral medicine, and also in the treatment of childhood disorders.

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.

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.

Behavior Modification,10/e assumes no specific prior knowledge about psychology or behavior modification on the part of the reader. The authors begin with basic principles and procedures of behavior modification and then provide readers with how-to-skills such as observing and recording. Next, the authors provide advanced discussion and references to acquaint readers with some of the empirical and theoretical underpinnings of the field. Readers will emerge with a thorough understanding of behavior modification in a wide variety of populations and settings.

The development of behavior modification principles and procedures and the ensuing research have had a dramatic impact on services for mentally re tarded persons. This book is the second edition of a volume that is designed to update readers on some of these many developments. Although many of the chapter titles and authors from the first edition remain unchanged, we have added additional chapters to reflect new areas of research. The book is thus a critical review of this literature and, as such, provides essential and important notions about what we know and what can be done to expand our current knowledge. The authors of the chapters are all recognized experts who have been active in publishing in the research areas they critique. As a result, they have a good understanding of what are the major issues in the field. And because they are also active in service provision to persons with identified handicaps, their material will be especially useful to practitioners and, it is hoped, to those_ professionals who are working in the field in estab lishing data-based treatments. One important change in the field has concerned the terminology used to We are aware that persons with mental retar describe handicapped persons. dation are no longer referred to as "the mentally retarded," and although no disrespect is intended, for the sake of continuity the original title has been retained on the advice of the publisher.