Abstract
This article offers a brief treatment of three interrelated topics pertinent to the conduct of long-term follow-up evaluations of early intervention. Initially, a number of conceptual and methodological issues are presented that address the following questions: (a) What is it that constitutes sound efficacy data? and (b) What are the essential elements of experimental control in long-term treatment evaluation? In the second section, these two questions are answered by a specific example of long-term follow-up research conducted at the Regional Intervention Program, Nashville, Tennessee. Included in this section are experimental procedures and results obtained on 40 former clients who were studied at 3 to 9 years away from active treatment. In the final portion of this article, a personal perspective on future efficacy research is offered.