Ten strains of C. jejuni each isolated respectively from patients with diarrhoea and from chicken intestine (10 strains from each source) were examined for presumptive colonization factor(s) by measuring their cell surface hydrophobicity and haemagglutination. None of the strains expressed cell surface hydrophobicity. However, 14 strains (7 from either source) showed variable haemagglutination pattern with human, sheep and rabbit erythrocytes in the presence of 0.5 per cent D-mannose. Thus, mannose resistant haemagglutinin(s) may be involved in the colonization of intestinal mucosal surfaces by C. jejuni.