A comparison of sonographic estimation of fetal weight and obstetrically determined gestational age in the prediction of neonatal outcome for the very low-birth weight fetus was conducted in a study population of 122 fetuses. With stepwise logistic regression, obstetric gestational age was found to be the best predictor of neonatal death, while sonographic estimated fetal weight did not add significantly to this prediction. However, both variables were important in the prediction of adverse neonatal outcome (neonatal death together with major neonatal complications of prematurity.