One of the major cause of recent acute viral hepatitis in Korean adults is hepatitis A virus (HAV) infection. Most of hepatitis A cases are young adults in their twenties or thirties, and the severity of the disease is related to the age of patients. The seroprevalence of HAV among the adolescents and young adults in their teens and twenties is about 10%, which suggests that a growing number of young adults are susceptible to HAV infection. Development of more adult cases with severe presentation is expected in the near future, and some preliminary data suggest the incidence rate of hepatitis A in Korea might be higher than 20/100,000 population. This clinical features and the epidemiological shift of HAV urge to promote childhood vaccination and consider catch-up vaccination for adolescents and young adults. More extensive evaluation on the nationwide epidemiology of HAV infection, cost-benefit analysis of HAV vaccination, and setting-up of guidelines for HAV vaccination are urgently warranted.