OBJECTIVES: The adverse health effects of mercury in dental amalgam have not yet been clarified. This study was conducted to examine the effects of dental amalgam on the concentration of blood mercury in Korean children. METHODS: A total of 1,275 students were enrolled in the elementary school in Seoul, Incheon, and Daegu. The number and location of dental amalgam filling of teeth were ascertained by oral examination. Dietary habits-including frequency of seafood intake-and other demographic factors were obtained from the children's parents. The concentration of blood mercury was measured by an atomic absorption spectrophotometer to which a hydride generator was installed. RESULTS: The geometric mean of blood mercury concentration was 1.91 microg/L. It was found that elementary school students in Seoul and the 4th grade elementary school students have the lowest concentration of blood mercury among the study groups. Both linear and secondary linear increase of the concentration of blood mercury, depending on the number of dental amalgam fillings, were statistically significant (p-trend < 0.01, p-quadratic < 0.01). As a result of multiple regression analysis on the blood mercury concentration of elementary school students, the regression coefficient (beta) of a dental amalgam filling was found to be 0.027 (standard error = 0.014, p = 0.048). CONCLUSIONS: In children, the dental amalgam fillings were significantly contribute to the concentration of blood mercury. To accurately assess the effect of dental amalgam on the concentration of body mercury, further studies using the concentration of urine mercury are needed.