An antibody-lectin enzyme immunoassay technique which had been developed for the analysis of sugar chains of alpha-fetoprotein (N. Kinoshita et al., Clin. Chim. Acta, 179: 143-152, 1989) was used for analysis of sugar chains of myeloma immunoglobulin G (IgG). The IgG sugar chains of four of nine patients with myeloma were found to be highly reactive to Lens culinaris agglutinin as compared with those of six normal controls and 177 patients without myeloma. This reflected a high L. culinaris agglutinin/concanavalin A ratio. The IgGs of these patients were found to have highly sialylated, fucosylated, and bisected biantennary sugar chains at Fab portions as judged by the lectin-blotting technique as well as by high-performance liquid chromatography analysis. These results indicate that some of the myeloma IgG proteins undergo unusual glycosylation processes.