Recent decades have seen the emergence of many new biobehavioral assessment tools for the newborn and young infant. These instruments have tremendous utility for scientists and practitioners engaged in exploring basic questions of development, studying medical and developmental conditions that place infants at risk, diagnosing the severity of biobehavioral insult, and evaluating the effectiveness of ameliorative interventions. Yet until now there has been no single volume providing an organized, critical examination of available assessment tools. Filling a crucial gap in the literature, this book describes a wide range of approaches to evaluating growth, sensation, arousal, regulation, learning, and attention in the prenatal period and the first year of life. Leading experts describe the historical background and development of each tool; review its diagnostic, methodological, and conceptual utility; highlight strengths and limitations for different uses; and consider broader implications for understanding the development of infants at risk.