BACKGROUND: As an endemic area of viral hepatitis B, many studies on hepatitis B and C have been reported in Korea, but no on all five viral types, A, B, C, D, and E. We surveyed ten serologic markers for the five different viral hepatitis and reviewed the seropositivity of each viral hepatitis and concurrent infection. METHODS: Ten serologic markers of five viral hepatitis (anti-HAV IgM, anti-HAV IgG, HBsAg, anti-HBs, anti-HBc, HBeAg, anti-HBe, anti-HCV, anti-HDV, and anti-HEV IgM) were tested for 260,488 samples requested for viral marker studies at three hospitals of Korea University Medical Centers from January through December, 2003. Anti-HAV IgM, anti-HAV IgG, anti-HDV, and anti-HEV IgM were tested by RIA and HBsAg, anti-HBs, anti-HBc, HBeAg, anti-HBe, and anti-HCV were analysed by ELISA or RIA method. RESULTS: Anti-HAV IgM and IgG seropositivity was 1.2% and 88.0%, respectively. Anti-HAV IgM seropositivity was high in a patient group 20 to 29 years of age. The overall seropositivity of HBsAg was 10.4% and for anti-HBs 60.4%. The seropositivity was 1.3% for anti-HCV, 1.1% for anti-HDV, and 22.2% for anti-HEV IgM. The concurrent positivity of HBsAg and anti-HBs was 4.0%. HBsAg was positive in 7 (0.1%) of anti-HCV positive patients; anti-HEV IgM was positive in 2 (25%) of anti-HAV IgM positive patients. CONCLUSIONS: Hepatitis A infection was rare in children but increased in patient group 20 to 29 years of age. The concurrent infection rate of hepatitis A with hepatitis E was high, suggesting that hepatitis E should be considered in hepatitis A patients. In view of the finding that the concurrent infection of hepatis B and C was detected, though at a relatively low rate, patients with viral hepatitis need to be assessed for the possibility of concurrent infection with other types of hepatitis.