We examined whether anti-Lewis x (Lex) and y (Ley) autoantibodies affect the pathogenesis of Helicobacter pylori-induced peptic ulcers. Of 11 patients with peptic ulcers, 10 patients had both anti-Lex and -Ley immunoglobulin G (IgG) antibodies, and 1 patient had only anti-Lex antibody. After successful eradication, we measured the serum titer of anti-Lex and -Ley antibodies. Six patients had a reduction of the titers of anti-Lex and/or -Ley antibodies, whereas no notable changes were detected in 5 patients in the follow-up. This result suggests that anti-Lex and -Ley autoantibodies had no critical role in the development of H. pylori-induced peptic ulcer.