The Gm(1), Gm(2), Gm(4), Gm(12), and Inv(1) factors were studied in the sera of 56 patients suffering from rheumatoid arthritis and 26 from various rheumatic diseases, by the hemagglutination inhibition test, using optimally reacting mixtures of Ragg and Nagg sera. The distribution of these factors was found to agree with that of healthy Greeks. No correlation was found between hypergammaglobulinemia and the discovery of the Gm(1) and Inv(1) factors. The presence of the rheumatoid factor was independent of the Gm and Inv phenotypes.