BACKGROUND: Hepatitis B is a worldwidely distributed disease. The hepatitis B prevalence of South East nations is reported to be higher than that of America or Europe. Korea is known to be one of high prevalent nation among Asia-Pacific nations. But hepatitis B prevalence in North Korea, separate from South Korea due to politics and ideology, is not reported. This study was performed using the data of North Korean defectors to estimate the prevalence of hepatitis B in North Korea. METHODS: We analyzed the data of 107 persons (98, mals, 9 females) who defected from North Korea and underwent screening exammination in a general hospital from July 1987 to March 1996. Twenty nine persons(25 males, 4 femals) were excluded because of incomplete data. The HBsAg test was carried out by reversed passive hemagglutination(RPHA) and the anti-HBs test was carried out by passive hemagglutination(PHA). The liver function tests were carried out by biochemical quantitative analysis method of Dimension. RESULTS: The study group were 73 males(93.6) and 5 females(6.4%). Mean age was 33.0+/-8.4 years and third decade was the largest as 35 persons(44.9%). The overall HBsAg positive rate was 15.4% and anti-HBs positive rate was 83.9%. Those who need vaccination was 51.4%. The only item amorg liver function tests which was statistically different by the hepatitis B viral marker groups was alkaline phosphatase. Mean total cholesterol was 176.4+/-38.0mg /dL. But no other item of liver function tests was statistically different in abnormal value by the hepatitis B viral marker groups. CONCLUSIONS: The overall HBsAg positive rate of North Korean defectors was much higher than that of South Korean and anti-HBs positive rate was much lower. So HBsAg positive rate of North Korean seems to be higher than that of South Korean. We think that a large study of hepatitis B for North Korean should be performed at every opportunity and take a measure to meet the situations.