Acute gastroenteritis is a leading cause of death in children throughout the world, with 3 to 6 million deaths estimated to occur annually in Asia, Africa and Latin America. Virus, bacteria, and parasite can cause an identical clinical syndrome, however greater than 75% of cases are caused by viruses. In acute sporadic and endemic childhood diarrhea, rotavirus, norovirus (NoV), sapovirus (SaV), human astrovirus (HAstV) and adenovirus (AdV) are the common causes; whereas most of cases are related to rotavirus and NoV in epidemic area. Children under 5 years of age are particularly prone, and it is calculated that, in this group, there are more than 700 million cases of acute diarrhea every year. The battle with diarrhea in Bangladesh goes back a long time before the independence of the country. Diarrhea, over the years, has killed millions of people and continues to be a major threat.This book describes the incidence of common viral pathogens responsible for gastroenteritis, seasonal distribution of viruses, age distribution of patients and molecular characteristics of etiologies among hospitalized infant and children in Dhaka City.