This final report describes a 3-year project which examined effects of different service delivery structures on the development of toddlers with disabilities who were receiving early intervention within natural group environments. Participants (n=70) were matched across four groups who were receiving either full-time specialized instruction or part-time consulting specialized instruction, and within each of these groups, were receiving therapy either within or outside of the natural group setting. Measures included indices of child development and social competence; family background, needs, use of community resources and social support; and the family's evaluation of their child's intervention program. Other measures documented intervention parameters within settings, specifically the type and intensity of specialized services, the quality of the intervention environment, type and quality of Individualized Family Service Plan goals and implementation, family involvement, and program costs. Evaluations were conducted every 3 months, beginning at 24 months and continuing through 36 months. Findings indicated that service location and modality were most consistently related to child development. Services provided at the early intervention center, in a group environment, and using a consulting model were related to greater developmental change than the alternatives. Fifty-two tables detail the study's findings. (Contains 11 references.) (DB)