98 Mexican Indians were tested for the blood properties A-B-O, A1-A2, M-N, P, Rh'-Rh''-Rh0-rh, and Hr. Of the 98 Indians, 90.8 per cent belonged to group 0, 6.1 per cent belonged to A1, and 3.1 per cent to group B. There were 61.2 per cent of type M, 3.1 per cent of type N, and 35.7 per cent of type MN. Of the 95 Mexican Indians tested with anti-P serum, 21.1 per cent were found to lack the P agglutinogen. In tests for the Rh blood types, 48.0 per cent of the Indians were found to belong to type Rh1, 9.2 per cent to type Rh2, 41.8 per cent to type Rh1Rh2, and 1 per cent to type Rh0. There were no bloods giving intermediate reactions. Of the 95 Indians tested for the Hr factor 44.2 per cent were found to lack this property. The reactions for the Rh blood types and Hr factor were correlated with each other and the results supported the conclusion of Race et al. that in addition to the six standard allelic genes and the so called intermediate genes, there is one or possibly two genes having the property of determining agglutinogens which react with anti-Rh' and anti-Rh'' sera, but not with anti-Hr serum. This gene (or genes) appears to be relatively common among Mexican Indians (approximately 3.3 per cent) in contrast to its rareness in white individuals.