OBJECTIVE To examine the relationship between lifestyles and psychosomatic symptoms in children, we conducted a self-administered questionnaire survey of elementary school students and junior high school students in Japan. METHODS We designed an original questionnaire to investigate the lifestyles and psychosomatic symptoms of children. In 1997, responses to the questionnaires were elicited from public elementary school fourth grade students (then aged 9-10) and public junior high school seventh grade students (then aged 12-13). The survey was repeated annually for three years as the students advanced through school. RESULTS For both boys and girls, each cross-sectional analysis revealed a strong relationship between lifestyle behaviors and psychosomatic symptoms. Psychosomatic, symptoms scores varied according to daily hours of sleep, eating of breakfast, having strong likes and dislikes of food, bowel habits, and daily hours of television watching. Both boys and girls with "good" lifestyle, behaviors evaluated by the HPI (Health Practice Index) showed lower scores for psychosomatic symptoms. CONCLUSIONS These findings show that the lifestyle behaviors of children are significantly associated with psychosomatic symptoms and suggest that poor lifestyle behaviors are likely to increase physical and psychological health risks.