This paper reviews major research dealing with the effects of infant/toddler day care on the behavior and development of infants, with special emphasis on useful research implications for those concerned with providing high quality group care for infants outside the home. A brief examination of major analytic issues dealing with the problem of developmental effects of infant day care focuses on variations in program objectives, the problem of defining and measuring the effects of the day care experience on children, and interpretive problems concerning the relationship between particular day care experiences and specific outcomes in children and families. A review of major research findings in the context of the above issues comprises the largest section of the paper. The review is organized around three primary categories which are affected by the day care experience: (a) intellectual or cognitive outcomes, (b) parent-child relationships, particularly maternal attachment, and (c) social relationships with other adults and peers. Final sections briefly summarize some of the principal research findings on the effects of infant/toddler day care and the implications of these findings for day care policy. Proposed are specific guidelines and policies to ensure quality day care which is supportive and facilitative of early child development and parent-child relationships. A concluding section discusses appropriate roles which could be played by the federal government in supporting early child care. (Author/CM)