The likelihood of survival to 28 days of life was determined retrospectively for 106 infants weighing less than 801 g at birth. Multiple logistic regression analysis revealed that birth weight and inspired oxygen fraction made an independent contribution to the prediction of survival at 8 h of age (predictive accuracy 76%). At 16 and 24 h of age, body temperature, pH, and the presence of spontaneous breaths were the independent variables predicting survival (predictive accuracy 79%). Of 37 infants with calculated chances of survival of less than 50% at 16 h, 29 died (predictive accuracy 78%). Seven of the remaining eight infants who survived "against the odds" either died later of chronic lung disease or had severe handicapping complications by 3 months of age. These predictions are first approximations and are not intended for use in making decisions about patient management.