Pseudomonas aeruginosa has been implicated in diarrheal conditions, and descriptions of these diseases date back as far as 1894 [1]. Some of these diseases have been described as 5-day or Shanghai fever [2], The use of ligated rabbit intestines for the demonstration of the accumulation of fluid by cultures of Vibrio cholerae was described as early as 1915 by Violle and Crendiropoulo [3]; the technique has been used extensively in recent years by De and Chatterje [4] as well as many other workers [5, 6] for the demonstration of enterotoxicities of various microorganisms. We have employed this technique to demonstrate the production of an enterotoxin by P. aeruginosa.