The paper reviews 16 studies on the effectiveness of active early intervention for Down's Syndrome children. An introductory chapter explains the nature and etiology of Down's Syndrome and reviews terms such as development and intervention. Chapter 2 analyzes studies in terms of influence of various types of intervention on developmental outcome in motor, cognitive, and overall functioning. Chapter 3 deals with the interplay of such variables as parent involvement and age of Down's Syndrome child at intervention. A final chapter cites methodological limitations of the studies yet concludes that the majority of studies found that early intervention was effective. (CL)