The presence of IgG antibodies reacting with Helicobacter pylori lipopolysaccharides (LPSs) in sera from children and adults diagnosed as H. pylori-infected, as well as healthy persons, was tested. There was no correlation between the production of antibodies reacting with H. pylori surface proteins and LPSs. Also no correlation between reactivity of tested sera with H. pylori antigens and deep rough mutant (Re types) enterobacterial LPSs was revealed. The prevalence of anti-LPS IgG in randomly selected children was relatively high.