The Apgar score has been useful for nearly four decades in focusing on five physiological signs (heart rate, respiratory effort, reflex irritability, muscle tone, color) that denote the condition of an infant during the first critical minutes of life. Before the development of the system, narcotic analgesia and sedation during labor, and general anesthesia for vaginal deliveries were commonly used. Research of the scoring method has focused on the effects of these interventions on the fetus and newborn and has been a major impetus for change in obstetric practices. The Apgar score has been used as a predictive index for neonatal mortality and morbidity and for later neurologic or developmental disability. Both the one- and five-minute scores are predictors of mortality in normal-birthweight infants, whereas in high-risk low-birthweight infants their score is limited. The score is an insensitive predictive index of long-term neurologic or mental handicap, and lacks both sensitivity and specificity to reflect accurately the degree of acidosis. It can be used effectively, however, if these limitations are understood and considered.