A solid-phase ELISA for Gm typing is described. A mixture of anti-Gm serum (or monoclonal anti-Gm antibody) and test serum was incubated in microtiter wells coated with IgG or its fragments of appropriate Gm type. After washing of the wells, the bound antibody was detected with peroxidase-labeled second antibody. The Glm(3), G3m(16), and G3m(21) antigens could be identified by this technique. Since some of the human anti-Gm sera and anti-Rh0 sera required for the conventional hemagglutination-inhibition method are hard to obtain, the ELISA system using anti-Gm antibodies and no anti-Rh0 sera may serve as an alternative to the conventional method.