Data were collected between February 2 and 17, 1998, from subject in grades 1 through 6, including students from all 33 public elementary schools, and subjects in grades 1 through 3, including students at 15 junior high schools in Tokorozawa, Japan. In all, 25,767 subjects responded to the questionnaire among 28,848 students. The response rate was 89.3%. Active parental consent for participation was obtained in the form of written permission.