Immunoreactive bands in sera from 81 Peruvian adults (48 females and 33 males) aged between 18 and 85 years were detected using enzyme-linked immunoelectrotransfer blot with a glycine-extracted Helicobacter pylori antigen. Sensitivity and specificity of bands were determined by comparison with results of H. pylori obtained by culture and silver stain of gastric biopsies. A crude antigen and a commercial enzyme-linked immunosorbent assay (Pylori Stat, Whittaker) were also evaluated for their diagnostic utility. H. pylori was detected in 57/81 (70%) of the subjects. The crude antigen enzyme-linked immunosorbent assay and the commercial enzyme-linked immunosorbent assay kits were, respectively, 84% and 88% sensitive. Specificity of both was 92%. The glycine-extracted antigen produced ten bands. The best single diagnostic band was at 20 kDa (83% sensitive and 96% specific). Three bands (13, 23, 30 kDa) were 100% specific. The combination of two diagnostic bands 20 and 30 kDa was 90% sensitive and 96% specific. Low molecular weight bands could be useful for the diagnosis of H. pylori infection.