The distribuiion of ABO and Rh blood groups antigens had been considered in 1305 people, personnel of the H. Colegio Militar in Mexico City, in 1967. Hematological data of three classified groups according to military rank have been analyzed: officials, cadets and regular soldiers. The distribution of phenotypes and genic frequencies in these military groups is interpreted as different levels of European admixture. Soldiers presented a high frequency of 0 type (high rate of gene r) and very few of Rh-type, which indicates an important. Amerindian component. On the other hand, Spanish admixture is larger in the groups as indicated by the gene A frequency Officials and cadets did not show significative differences in the frequency of the 0 blood type, but soldiers present statistical difterences with other groups (X² =11.5, P < 0.005). If social origjn is considered, these military groups show a parallelism in admixture level and social stratification. This fact suggests the necessity to consider the social origin in order to approach the study of genetic structure in Mexican populations.En esta investigación se pretende brevemente analizar la distribución de tipos sanguíneos de una muestra mestiza de militares que pertenecen a la Ciudad de México.