Over 200 articles have been published describing behavior modification programs for weight reduction. We reviewed the group studies that reported weight data at least 1 year posttreatment. Evaluating these studies, we concluded that although changes in weight do occur, these changes are almost always clinically small, variability among patients is large, and further weight losses do not occur following the end of formal treatment. The weight lost during treatment may be explained by changes in specific eating behaviors caused by therapist contact rather than the effect of self-applied behavioral techniques on eating. Support for the effectiveness of each of the specific techniques to produce lasting weight loss or behavioral change was also lacking. Suggestions for future research in this area are given.