This study was conducted to evaluate the effects of lead concentration in the blood on intelligence and personality in school children in Korea. This study was designed as a cross sectional study. The Korean Intelligence Test-Primary was administered to the 302 school age children (154 3rd-grade and 155 6th-grade) of three areas, urban, fishery, and agricultural area, Korea. Blood lead (Pb-B) was measured by means of atomic absorption spectroscopy equipped with graphite furnace atomizer. Geometric means of Pb-B for boys and girls were $2.79pm1.58{mu}g/dL$ and $2.54pm1.51{mu}g/dL$, respectively. No children exceeded Pb-B of $10{mu}g/dL$ that is the recommended level of Pb-B in children by CDC, U.S.A. When the subjects were classified by median into two groups, upper and lower Pb-B groups, the IQ of upper and lower groups were $106.4pm13.7$ and $110.0pm14.9$ respectively. IQ score of upper group was lowered about 4 points than that of lower group. We founded that hyperactivity and autism score of Pb-B groups was higher than that of lower group. These results are coincident with the large-scale study results developed countries that chronic exposure to lead may reduce the intelligence of child. This study may provide the first suggestive evidence that Pb-B has an impact on childhood intelligence and personality in Korean children. It is necessary to consider the effects of other important factors, such as parental intelligence in the next study.