This volume examines the importance of prenatal, birth, and postnatal factors in determining the extent of "risk" that may be predicted for an infant in the first year of life and in early childhood. It offers the reader an up-to-date review of major research efforts toward understanding the circumstances that insure optimal developmental opportunities for all children. In the first chapter, Dr. Horowitz presents some of the basic issues concerning vulnerability of young infants and developmental hazards. Papers by Arnold Sameroff and Herbert Leiderman consider early infant-environment interactions as they relate to normal developmental processes and social bonding. Lewis Lipsitt examines data from the Collaborative Perinatal Project and from studies on Sudden Infant death Syndrome to propose some factors that contribute to the SIDS phenomenon. Trygg Engen reviews his research on the conditions that influence children to ingest harmful substances. The concluding chapter considers the implications of these papers for understanding environmental and biological conditions as they affect the developmental course of the infant and young child.