The purpose of this study was to describe a research project that investigated an alternative service delivery model for infants, toddlers, and their families who were eligible for early intervention services under Part C of the Individuals with Disabilities Education Act (IDEA). These families were of Latino heritage and had Spanish as their preferred and dominant language. The study included children representing a range of types and levels of disability and behaviors, and families of differing socioeconomic status, all of whom were English language learners. The research design contained an experimental comparison of two service delivery models: traditional early intervention; and early intervention designed to promote learning within family-defined activity settings. Measures were implemented with both groups of children and families yearly for at least two years. Measures included indices of child development and behavior, family background, beliefs, and experiences, and service delivery characteristics, including cost, the use of natural environments for learning, types and intensity of specialized services, type and quality of Individualized Family Service Plan (IFSP) goals, and English language use in activity settings. The last outcome was measured across both parents and children, as the first years of a child's life seem to be the optimum time for dual language learning. Appended are: List of Measures, Procedural Manual, and Measures for Phase I, Phase II, and Phase III, respectively; Brochures; Results Tables for Phase I, II, and III, respectively; and Phase III Results Figures. (Contains extensive references.) (Author)