Work on the instrument grew out of research on newborn assessment and training for the Perinatal-20 Project, a series of 20 intervention studies of drug abusing-mothers funded by the National Institute on Drug Abuse. The NNNS provides a comprehensive examination of normal full-term infants, preterm infants, and especially infants at risk because of prenatal drug exposure. Although a precise lower gestational age limit cannot be set, the examination is appropriate for infants as young as 34 weeks. The instrument's reliability has been demonstrated, and its concurrent and predictive validity is being evaluated in the Maternal Lifestyles Study of 1,000 infants. Steps followed in developing the instrument are outlined, along with scoring refinements and administration procedures. 18 references