Hepatitis A virus (HAV) infection is the most frequent cause of viral hepatitis worldwide. HAV belongs to the Picornaviridae family in the genus Hepatovirus. The genome of HAV is a positive-sense single-stranded RNA that is approximately 7.5 kb in length. In fact, HAV is classified into six genotypes: three isolated from humans (I–III) and three of simian origin (IV–VI). Worldwide, genotype I is the most prevalent, particularly subgenotype IA. A diagnosis of hepatitis A can be performed by detection of anti-HAV IgM and IgG antibodies by enzyme immunoassay or HAV RNA detection by nested-PCR. Hepatitis A is transmitted principally via the fecal-oral route, including person-to-person contact and the ingestion of water or food that is contaminated by the feces of infected individuals. HAV infection is usually selflimited and benign, with no symptoms, but a severe form of the disease, fulminant hepatitis, affects approximately 1% of the patients who are hospitalized for hepatitis A. In Latin America, several seroprevalence studies have demonstrated an epidemiological shift in HAV infection from high towards intermediate endemicity levels. In Brazil, a large number of children under five years of age (74.1-90%) have been found to be susceptible to HAV infection in 3 capitals of the North, Midwest and Southeast region of Brazil. There is no specific treatment for hepatitis A. Therapy should be supportive and aimed at maintaining an adequate nutritional balance.