β2-Glycoprotein I typings on 152 healthy Germans and 150 patients with atopic diseases did not show any differences in the serum protein concentrations or in the phenotype and gene frequencies. Compared to these German samples, Philippinos (n = 88) as well as healthy Negroes from South Africa (n = 192) revealed statistically significant lower concentrations of this serum protein. They differ also from the Germans with regard to phenotype and gene frequencies. A most striking result was found in the comparison of healthy and leprous Negroes (n = 250) from South Africa. In these, quite different and statistically significant β2-Glycoprotein I concentrations, respectively, phenotype and gene frequencies were seen, which may be due to this disease. The possible reasons for these observations as well as for the observed population differences are discussed.