This chapter provides an overview of some of the problems related to gastroenterology and hepatology. Acute diarrhea (AD) can be classified as acute watery diarrhea (AWD) and acute dysentery. Hydration status is classified according to WHO as no dehydration, some dehydration and severe dehydration. Most infants and children with mild and moderate dehydration can be managed safely with oral rehydration therapy (ORT) alone. Diarrhea is considered as a nutritional disease and the outcome depends on the nutritional status of the child. The weight of the child should be recorded. This helps both in calculating fluid requirements and also assessing the nutritional status. The macroscopic examination of the stools by the pediatrician in relation to volume, color, presence of blood and mucus is more useful than a microscopic examination. Sepsis, bronchopneumonia, urinary tract infections (UTI) and acute suppurative otitis media are the associated infections which predispose AD progressing to persistent diarrhea. Viruses are the most important causative agents of hepatitis and the term viral hepatitis refers to the illness caused by the major hepatotropic viruses—hepatitis A, B, C, D, E though several other viruses such as coxsackie viruses, Epstein-Barr virus, herpes simplex and cytomegalovirus (CMV) can cause hepatitis. The etiological diagnosis is made by the presence of immunoglobulin M (IgM) specific antibodies e. g. HAV by anti-HAV IgM, HBV by hepatitis B surface antigen (HBsAg) and anti-Hepatitis B core (anti-HBc) IgM, HCV by anti-HCV IgM and HEV: anti-HEV IgM. Children with acute hepatis B should be followed for 6 months for HBsAg seroconversion. All children with acute liver failure need intensive care support to prevent further deterioration and to treat the complications. Parasitic diseases may be due to protozoa or helminths. Helminthiasis or worm infestation of gastrointestinal tract (GIT) is a common problem in children in tropical countries. They are more often present in children living in conditions with poor hygiene, lack of proper sanitation, potable water supply and overcrowding. Gastroesophageal reflux disease (GERD) is the clinical and pathological consequences of GER affecting the esophagus, respiratory tract or oropharynx.