BACKGROUND: Recently, some outbreaks of hepatitis A have been reported in Korea. Comparisons of VP1/P2A sequence of hepatitis A virus (HAV) are useful in identifying a specific strain, its genotype, and geographic distribution of HAV. We performed nested reverse transcription-PCR (RT-PCR) and direct sequencing of HAV to investigate a molecular epidemiology of an outbreak of HAV infection. METHODS: Stool specimens collected from 24 patients during a hepatitis A epidemic were examined. Nested RT-PCR, targeting the VP1/P2A region, was performed. The RT-PCR products from six samples were sequenced to evaluate the genetic relatedness among the strains. RESULTS: HAV RNA was detected in 16 of 24 patients with hepatitis A. All of the six tested for HAV strains showed a 100% nucleotide identity and were classified as subgenotype IA by phylogenetic analysis of the VP1/P2A region. CONCLUSIONS: Analysis of the HAV VP1/P2A region suggested that a single HAV strain caused the outbreak. Korean HAV strains from this study belong to subgenotype IA, which is the prevalent type in the world.