This review focuses on diarrhea caused by toxins released by enterotoxigenic Escherichia coli. These bacteria are known to produce toxins that have adverse effects on the intestinal tissue in Man and animals. E. coli is contracted through the ingestion of water or food contaminated by this bacterium. Generally, E. coli colonizes the intestinal mucosa where it multiplies and causes damage to the target cells or interferes with the homeostasis that prevails in the gastrointestinal tract. Enteropathogens such as E. coli are only able to exhibit their effects after colonization of the intestinal mucosa from where they release their toxins. These bacteria mainly affect chloride ions secretion through second messenger pathways resulting in secretory diarrhea. In this review, the association of bacteria with the gastrointestinal tract as pathogens and the resulting effects on the various systems of the intestine, including the nervous system and mediators leading to secretion and diarrhea are examined.