This chapter seeks to familiarize the reader with gastrointestinal infections and cover discussion on bacterial and viral gastroenteritis. The most frequent symptoms are diarrhea with or without nausea, vomiting and fever. Onset of gastrointestinal tract (GIT) symptoms within 6 hours of ingestion suggests a preformed toxin such as Staphylococcus aureus and Bacillus cereus food poisoning, whereas symptoms due to most infections caused by ingesting viable bacteria develop 24–72 hours following ingestion. Viral infections, noninvasive bacterial infections and many parasitic infections generally resolve without antimicrobial therapy. Bacterial gastroenteritis includes Campylobacter Infection, Clostridium difficile infection, botulism, Escherichia coli, Salmonella, Shigella, Vibrio infection, Yersinia infection, and Helicobacter pylori which are briefly discussed in this chapter. Viral gastroenteritis remains, globally, a significant cause of acute gastroenteritis and the leading cause of death among young children. Rotavirus and noroviruses are the two most common causes of viral gastroenteritis.