Investigation of the etiological relationship between body fat and uterine leiomyomas.This was a case-control study. Percent body fat was measured bioelectrically with a body fat analyzer.In Sapporo City, Japan, 100 women with uterine leiomyomas (pathologically diagnosed) and 200 controls who were confirmed to have no uterine leiomyomas by clinical examination.Among the four types classified by BMI (over/under 24.0) and percent body fat (over/under 30%), the occult obesity type (BMI or = 30%) had the highest risk. There were no patients of muscular type (BMI > or = 24.0 and percent body fat < 30%). Women with more than 0.80 of waist-to-hip ratio were also at significantly higher risk.Occult obesity and upper body fat distribution may lead to the development of uterine leiomyomas.