The Caesarean sections at the Universitäts-Frauenklinik Innsbruck from January 1st, 1969 to December 31st, 1974 have been surveyed. Related to the total number of 12 579 deliveries 627 Caesarean sections have been performed. Two 3-year-intervals have been compared: 1969-1971 (group I) without and 1972-1974 (group II) with modern practices of prenatal supervision. There was a high significant increase of the section rate in group II (5,8% versus 4,1% which has been related to the increasing number of mainly fetal indications. The maternal morbidity didn't rise with the increasing section rate. A significant decrease in total infant mortality rate and mortality rate at vaginal deliveries has been found with the increasing incidence of Caesarean sections; whereas the number of depressed infants (Apgar score less than 7) was increased in group II. The reasons therefore have been discussed. The rise of the number of Caesarean sections in group II performed because of breech presentation (14,2% versus 6,2%) was correspondent with a statistically significant decrease in the mortality rate from 11,7 to 4,1%. A Caesarean section rate between 7% and 10% seems to be the limit at least in our hospital--the total infant mortality rate cannot be reduced by further increasing the section frequency: the infant mortality rate possibly could be lowered by a better and more wide spread prenatal care especially by taking more care for prematurity and by intensifying the perinatal period.