In a retrospective study performed at the university department of pediatrics at Aachen the development of the mortality rate of extreme low birth weight infants (less than or equal to 1000 grams) born from 1976 to 1987 has been under investigation. During this period a decline of the neonatal mortality rate from 79.5% to 29.8% could be observed. Sex, gestational age, birthweight, place of birth and delivery mode were important factors influencing the outcome of the patients. Premature babies who were born by caesarean section had a significantly higher survival rate than babies who had been delivered vaginally. Premature babies born in the university hospital at Aachen (inborns) had a remarkably lower neonatal mortality rate than infants who postpartum had been transferred to the intensive care unit from surrounding hospitals (outborns). A second aspect of this study was the development of neonatal morbidity. For some diseases like intracranial hemorrhage a decrease in frequency could be noticed. Especially high-graded intraventricular hemorrhage (IVH greater than or equal to III degrees) occurred significantly less frequent between 1985 and 1987. The comparison of morbidity rates between inborns and outborns revealed a lower incidence of hyaline membrane disease, pneumothorax and intracranial hemorrhage in inborn patients. The results of this study imply that the intensive care of extreme low birth weight infants is justified. To achieve even lower mortality and morbidity rates the importance of regionalization has to be emphasized.