An overview is provided of a 5-year project conducted by the Early Intervention Research Institute (EIRI) which focused on the effects and costs of early intervention for young handicapped children. The bulk of the document consists of research reports of 14 investigations: (1) meta-analysis of the early intervention efficacy literature; (2) cost-effectiveness of half-day and full-day preschool special education programs; (3) early intervention with hearing impaired children; (4) cost-effectiveness of paraprofessionals versus professionals in early intervention; (5) cost-benefit analysis of the Abecedarian program; (6) quantitative synthesis of single-subject research; (7) cognitive intervention with developmentally delayed preschoolers; (8) effects of differing levels of parent involvement on preschoolers' development and behavior problems; (9) intervention for infants with intraventricular hemorrhage; (10) cost-effectiveness of parent and clinic early intervention for children with language handicaps; (11) analysis of special education early childhood projects approved by the Joint Dissemination Review Panel; (12) economics of early intervention; (13) follow-up study on intraventricular hemorrhage; (14) Down Syndrome parent involvement. Activities of the EIRI in improving the quality of efficacy research, influencing early childhood legislation, and making practitioners and researchers more aware of the importance of collecting both costs and effects data in the early intervention field are also discussed. (JW)