This report is the fourth in a series of follow-up analyses of nine longitudinal studies addressing the costs and effectiveness of alternative types of early intervention for children with disabilities. An introduction provides an historical perspective and conceptual framework for the studies, including common study elements and how research sites were selected. Focus of the studies has been on effects of varying the intensity of the intervention, effects of beginning intervention at different ages, and effects of variation in program components. A summary is provided for each study consisting of, first, information about the alternative forms of intervention being examined, and, second, a graphic summary of the outcomes for the various measures of child and family functioning. The bulk of the report consists of individual site reports in which each include a rationale, methodology, results and discussion, and conclusions. The individual studies are: (1) the New Orleans Visual Impairment Study (which varied the intensity of family involvement); (2) the SMA/LakeMcHenry Intensity Study (which varied the frequency of intervention services); (3) the Arkansas Intensity Study (which varied the frequency of home-based interventions by paraprofessionals); (4) the Jordan School District (which varied the frequency of a center-based intervention and the adult/child ratio); (5) the Salt Lake City Medically Fragile Study (which varied the age at which sensorimotor intervention was begun); (6) the Charleston, South Carolina Medically Fragile Study (which also varied the age of beginning intervention); (7) the Columbus Medically Fragile Study (which varied the intensity of intervention); (8) the Des Moines Public Schools Study (which compared center-based interventions with and without a parent education component); and (9) the Utah Parent Involvement Study (1986) (which also compared center-based interventions with and without a parent education component). Contains 272 references. (DB)