Aims: To relate the diseases caused by strains of Salmonella paratyphi B and S. java to pathogenic mechanisms expressed by these bacteria for the purpose of organism discrimination. Methods and Results: Epidemiological data relating to cases of disease caused by strains of S. paratyphi B and S. java , isolated over a 10-year period, were analysed with respect to patients' symptoms, particularly those involving enteric fever. Strains of S. paratyphi B and S. java were also examined for a range of known pathogenic mechanisms. Infection with S. paratyphi B involved pyrexia in 12.5% of patients compared with 2.2% of patients infected with S. java . These organisms could not be differentiated based on the pathogenic properties examined. Conclusions: Strains of S. paratyphi B appear not to be a major cause of enteric fever but primarily a cause of gastroenteritis, in common with S. java . Both organisms express similar pathogenic mechanisms, and strains of S. java are probably d -tartrate utilizing variants of S. paratyphi B. Significance and Impact of the Study: Strains of S. paratyphi B are very closely related organisms, primarily causing gastroenteritis. From this study it would appear that strains of S. paratyphi B are not a major cause of enteric fever.