Providing an optimal program of early intervention for young children with developmental disabilities and their families requires knowledge of reliable and current information on research and practice. However, analyzing research studies and determining their relevance to practice can be a perplexing task, even for the professional. Differing methodologies and a variety of conceptual frameworks often make it difficult to judge the quality of the research and to discern outcome patterns that can—and should—influence practice.  Despite the fact that this is a difficult task, practice guidelines based on a sophisticated and rigorous analysis of the extant research literature can convey essential information for the design and implementation of optimal early intervention programs.