Several basic principles undergird the components of the model programs profiled. They are two-generational, in that they meet the needs of parents of very young children so they are able to deal with the demands of early parenthood. The programs are comprehensive; they recognize that wherever the point of entry into services occurs, families must be provided with services directly or through formalized linkages to other services if their multiple needs are to be met. The model programs are also continuous, in that the assessment of a young child's needs and those of their families is an ongoing process. Successful programs are developmental, as they facilitate positive interaction between parent, child, and caregiver. Well-designed models focus on the content and quality of care as well as service availability. An increasing number of model programs recognize that the primary prevention strategy for infants and toddlers is to strengthen the small child's immediate environment of the family, other significant adults, and the neighborhood. Model programs for young children and their families are also accessible and sensitive to culture and ethnicity. The specific model programs described are categorized as community-based models, school-based models, and health-based models.