To provide current clinical information for obstetric decision-making and perinatal management, we present early morbidity and mortality data for extremely premature infants based on obstetric assessment of gestational age. We reviewed the records of 141 live-born infants with birth weights of 1600 g or lower born at a university hospital level III neonatal intensive care unit between January 1986 and April 1988, whose gestational ages estimated by antenatal obstetric evaluation were between 24-29 completed weeks. Neonatal survival to 30 days ranged from 20% at 24 weeks to 94% at 29 weeks. Chronic lung disease was present at 30 days in all infants born at 24 weeks' gestation, decreasing to 13% of infants born at 29 weeks' gestation. Rates of severe intraventricular hemorrhage (grade 3 or 4) ranged from 100% at 24 weeks to 7% at 29 weeks. These data represent a significant increase in survival and a decrease in early morbidity compared with those form similar populations before 1986.