Out of 10,000 cases delivered at the Department of Obstetrics and Gynecology, Okayama University Medical School during the period from April 1934 to November 1957, the author conducted statistical observations on 29 cases of prolapse of the umbilical cord from various viewpoints; and obtained the following results. 1. The incidence of prolapse of the umbilical cord is 0.29 per cent being lower than that formerly encountered. The incidence of the prolapse in primpara and grand-multipara is significantly higher than that in multipara. In the age range below 29 years old and over 30 years there is no significant difference in the incidence. Looking at from year to year, the incidence of prolapse of the umbilical cord is on the increase, and from the duration of pregnancy the incidence in premature labor is low. 2. As for the causes the abnormal presentation, premature baby, the shift of the presenting part due to Metreulysis or Colpeurysis, abnormally long umbilical cord, early rupture of membrane, contracted pelvis, enlarged pelvis, placenta preavia and so forth can be pointed out. 3. Hardly any disturbances can be recognized in the mother. 4. The mortality rate of infants with prolapse of the umbilical cord. a. The prognosis of such infants is extremely poor, amounting to 44.44 per cent of the total mortality, while the mortality rate of the infants still living at the time of discovery of the prolapse amounts to 44.0%. This is somewhat lower than the formerly reported rate, still it is quite high. b. There seems to be no marked relationship between the mortality rate and the frequency of labors, but it tends to show a higher rate in older women. c. The mortality rate is highest in transverse presentation followed by cephalic presentation and breech presentation in the order mentioned. In breech presentations foot presentation can not be said to be always good in the prognosis. d. The mortality rate is generally high in abnormally long umbilical cord. e. It is higher in spontaneous rupture of membranes than in the artificial rupture. f. Speaking from the height and the movableness of the presenting part, the mortality rate is highest in those engaged in pelvic inlet or slightly engaged in pelvic inlet, but it becomes lower in the order of those with the mouable head above pelvic inlet, with the head in pelvic expantion, and in plane of pelvic contraction and plane of pelvic outlet. g. The mortality rate is higher in ones with poor dilatation of the uterine orifice than in those with the complete dilatation. h. As for the treatment of prolapse of the umbilical cord, since the mortality rate is higher in the case requiring a longer period of time for delivery and expectant treatment such as reposition of cord is unsatisfactory, it is desirable to give abdominal caesarian section as far as it can be indicatad. i. The longer the duration from the onset of labor to expulsion the poorer is the result. For this reason, it is necessary to discover prolapse of the umbilical cord earlier and what is more, the care must be excercised so as to prevent its occurrence.