Acute diarrhea defined as an increased frequency of defecation (more than 200 g of stool per day). Noninflammatory diarrhea is characterized by watery stools. Because of the morphology of the intestinal mucosa is normal or only minimally altered, stools do not contain leukocytes and blood or only a few leucocytes and occult blood. Noninflammatory diarrhea is caused various bacteria, viruses, and protozoa. In this review article, the roles of bacteria, such as enterotoxigenic Escherichia coli, Vibrio cholerae, Clostridium perfringens; viruses, such as Rotavirus; and protozoa, such as Giardia and Cryptosporidium in the pathogenesis of noninflammatory diarrhea have been discussed.