The sudden, silent, unobserved death during sleep of an apparently healthy infant strikes about 8,500 children each year in this country. Once called crib death, sudden infant death syndrome (SIDS) has left a trail of grieving parents and baffled pathologists who could find no specific cause at autopsy. One current theory links apnea of infancy to this mystery killer. In the first article of this series on pediatric problems, Dr Goldhagen, who directs an infant apnea evaluation program in Minneapolis, discusses a practical approach to identifying and managing children at risk for apnea of infancy and offers suggestions on the use of cardiorespiratory monitoring in the hospital and in the home.