Acute infectious diarrhea is the most common cause of diarrhea worldwide and is the leading cause of deaths in childhood. Despite improvements in public health and economic wealth, the incidence of intestinal infection remains high and continuous to be an important clinical problem in developed countries. Acute diarrhea, defined as an increased frequency of defecation (three or more times per day or at least 200 g of stool per day) lasting less than 14 days, may be accompanied by nausea, vomiting, abdominal cramping, clinically significant systemic symptoms, or malnutrition. Acute infectious diarrhea presents clinically as one of two major clinical syndromes, acute watery diarrhea, which usually resolves within 5~10 days, and diarrhea with blood (dysentery). The initial clinical evaluation of the patient with acute diarrhea should focus on the assessment of the severity of the illness, the need for rehydration, and the identification of likely causes on the basis of the history and clinical findings. In this article I focus on the causative agents, diagnosis, and management of acute infectious diarrhea in immunocompetent adults in Korea.