The paper was written to document the importance and efficacy of comprehensive early intervention services for children with special needs and their families; to serve as a resource to a wide range of agencies, organizations and individuals concerned about the needs of special needs children and the families; and to advocate support at all government levels for providing accessible, continuous, high quality services beginning at birth for children with special needs and their families. Section I includes reviews of research which demonstrates the effectiveness of intervention programs and their impact on the development of very young handicapped children and on infants and toddlers at risk. Early intervention research findings are reported in relation to motor development, emotional and social development, language development, cognitive development, specific populations (such as the mentally retarded and severely/profoundly handicapped), and newborns. Section II describes the effect of services on the family, identified family service needs, and the rationale for the participation of families in programs for handicapped infants and toddlers. A third section shows data on the costs and cost effectiveness of intervention programs for children aged birth to 3 years, and the fourth section outlines the characteristics of a comprehensive service delivery system followed by specific recommendations for action at local, state, and federal levels. Tables and charts offer statistical data on special education costs. (Author/SB)