For a better definition of the factors which could be at the origin of neonatal distress, 357 cases of mono-fetal term pregnancies with breech presentation were retrospectively studied between January 1st, 1984 and December 31st, 1989. The population is identical to that of all deliveries except for a higher percentage of first pregnancies. The risk of emergency caesarean section mostly concerns large primiparous women, underweight, with normal or large pelvis. Caesarean section is absolutely necessary if the biparietal diameter exceeds 100 mm, if the head is positioned in hyper-deflection and/or if the pelvis is defective. Without being mandatory, the procedure is preferable in case of chronic fetal distress or scarred uterus. On the contrary, neither the age of the mother nor the age of the pregnancy, nor the type of the breech, nor the number of pregnancies have any effect on the prognosis. The current rate of caesarean section is 47.9 per cent with almost complete disappearance of the large breech extraction (0.6 per cent) and the Mauriceau's maneuver (0.3 per cent). The corrected mortality rate is 0.28 per cent. In addition to the parameters considered in our coefficient of risk of breech delivery, it was noted that a pre-pregnancy weight exceeding 70 kg or a weight gain of more than 15 kg represent unfavorable factors. It is desirable to calculate prospectively the severity of the risk in small size cases, when the biparietal diameter ranges between 96 and 100 mm, or when one of the diameters of the bony pelvis is decreased.