Statistics on more than 120,000,000 cases of labor were obtained from official sources in 21 countries, and the percentages of the various types of multiple births were computed from them. The percentage varies greatly for different countries. The twin percentage ranges from 1.59% in Denmark to .40% in Colombia, and the triplet percentage from .0185% in Denmark to .0040% in Greece. Twin confinements occur once in 85.2, triplet confinements once in 7,628.7 and quadruplet confinements once in 670,734 cases of labor in this study. These results agree essentially with findings of the earlier and less extensive investigations of Guzzoni and of G. Veit and also with the estimate of Arey. This agreement seems to indicate a fixed relationship between the incidence of the various types of human gestations. A general agreement was noted between the twin and triplet percentages in the individual countries. Those countries having a large twin percentage had also a large triplet percentage, while those reporting few cases of twins reported also few cases of triplets. The total twin, triplet, and quadruplet ratios were found to be respectively 1:85.2; 1:(87.3)2, and 1:(87.5)3. These values very closely approach those expected according to Zeleny''s hypothesis that, if 1/n is the proportion of twin births to all births in a large population, then the proportion of triplet births and the proportion of quadruplet births for the same period will approximate respectively 1/n2 and 1/n3.