Aeromonas hydrophila was enteropathogenic in ligated ileal loops of rabbits, causing a fluid accumulation of 14-2.0 ml per cm of gut length. Gut reaction could be produced with an inoculum as low as 104 viable bacteria. There was no difference in the nature of the positive reactions given by strains isolated from diarrhoea1 and non-diarrhoea1 children and adults and from water. Plesiomonas shigelloides, on the other hand, did not cause a significant gut reaction. A. hydrophila multiplied in the ileal loop by about 105 whereas P. shigelloides did so at only 102-3. These experiments on an animal model thus indicated the enteropathogenic nature of A. hydrophila, but no definite conclusion could be drawn from this study on P. shigelloides.