There are few reports on lead exposure in children living in the center and the suburbs of large cities. As subjects of epidemiological investigations on the effects of lead exposure in ambient air, school children are very significant in that they have a relatively limited sphere of movement in their daily life. In a previous study the authors compared school children living in the center of Tokyo and those in a suburb of the city and reported that the blood lead levels (PbB) were significantly higher in children living in urban areas [12]. However, it was concluded that further investigation of factors other than ambient air was required to determine the cause of this difference. In the present study, the method used was the same as that of the previous study. However, the areas investigated in the present study were distant from those of the previous study. The results again indicated that the average PbB of school children in the city-center was approximately 2.5–4.8 mg/100 g higher than that of suburban school children, a statistically significant difference. An analysis made on the combined data from both studies according to age revealed that urban school children indicated the highest level among younger urban children, showing a gradual decrease in lead levels as age increased (from 10 to 15 years of age). Suburban children did not show this decline. As a result, it was concluded that these differences in PbB might not be attributable only to lead exposure in ambient air, but to lead exposure from sources such as street dust to which young children are more readily exposed than adults.