Several agents were employed to induce diarrhea in squirrel monkeys: (1) diarrhaogenic diets, (2) various doses of cholera toxin, (3) prostaglandin derivatives, (4) bile, (5) lactulose, (6) phenolphthalein, (7) castor oil. Kaolin, pectin, Kaopectate and placebo were used as antidiarrheal treatment. Evaluation was based on (a) frequency, (b) consistency, (c) total and dry weight of the stools, and (d) electrolyte loss. The spectrum of procedures employed appeared to be suitable for the evaluation of antidiarrheal agents of the protective and adsorbent class.