Diarrhea is defined as the passage of three or more loose or liquid stools per day. It is the second most common cause of death in children less than five years of age. Around 1.7 billion cases are be–ing reported every year. It can be acute, persistent or chronic depending upon the duration. Chronic diarrhea in developing countries is often due to intestinal infection that lasts longer than expected. In developed countries chronic diarrhea due to infectious cause is less common and its etiology is more diverse. It may be secretory or osmotic based on the underlying mechanism. Diarrhea per se can lead to malnutrition in children. With each episode their malnutrition status worsens. On the other hand, malnourished children having impaired immunity are at more risk to develop life threat–ening diarrhea. Most children with fatal diarrhea, dying from severe dehydration and fluid loss, of–ten have underlying malnutrition as well. Diarrhea is both treatable and preventable. In developing countries like India it is mostly related to gastrointestinal infection and can be prevented by measures such as provision of safe drinking water, improved sanitation, personal hygiene, health ed–ucation, promoting breastfeeding and rotavirus vaccination. Diarrhea can be treated by rehydration with ORS solutions along with zinc supplementation and by intravenous fluids in conditions associ–ated with severe dehydration and shock