The lipopolysaccharide antigenicity of 22 Salmonella strains (representing nine serogroups) and four non-salmonellae Enterobacteriaceae to the Salmonella genus specific monoclonal antibody M105 was analysed. The monoclonal antibody M105 reacted with all 22 Salmonella strains. Probing SDS-PAGE separated LPS molecules with MAb M105 revealed that the antibody reacted with the core region of all Salmonella serovars. However, no reaction was obtained to the long-chain LPS of serovars O (Salm. adelaide and Salm. ealing), C1 (Salm. infantis, Salm. livingstone and Salm. virchow) or Salm. arizonae. It is plausible that the presence of a second core antigenic type results in the lack of reaction between long-chain LPS and the Salmonella genus specific monoclonal antibody M105.