Since its inception, the study of childhood intervention has had a variety of goals; some have been realized, and some have not. In addition, research has contributed a wide variety of unanticipated but extremely beneficial outcomes of intervention programs, and, as a result, additional programs have been mounted to produce these once-unexpected benefits. Experiences such as these have taught workers to evaluate carefully not only outcomes, but intent as well. Although our most general goal—to improve children’s lives—has remained constant since the earliest days of intervention plans, in more recent years the emphases of programs and evaluations have changed to reflect our increasingly sophisticated understanding of the broad effects of intervention and of the variables which mediate these effects.