Forearm bone mineral content for adult white elite synchronized swimmers is lower than that of normative data (Roby et al. 1988). However, bone mineral density (BMD) in local body regions and the body as a whole are unclear in adolescent synchronized swimmers. The purpose of this study was to examine BMD of adolescent synchronized swimmers. This study also examined the relationship between BMD for young athletes and biological (e. g. morphological and functional aspects) and habitual (e. g. physical activity and nutritional state in daily living) variables. Subjects were nine females selected nationwide out of a large number of synchronized swimmers of fourth to sixth grade in elementary school, who participated in an audition with the committee of synchronized swimming in the Japan Swimming Federation. Chronological and bone age were 13.4±1.0 years and 12.7±0.9 years (n=8), respectively. BMD was evaluated in local regions and the body as a whole by dual X-ray absorbtiometry (DXA). Walking was measured by pedometer, and physical activity and nutritional status were analyzed by activity diary and food weighing method, respectively. As a result, mean BMD in athletes tended to be lower than in normal Japanese girls for lower limbs and lumbar vertebra (L2-L4), while it was almost the same between the two groups for whole body, upper limbs, thoracic vertebrae and pelvis. The correlations between BMD for whole body and bone age, the number of years since menarche, body mass, lean body mass and physical activity in leisure time of daily life were significant. An analysis using a general linear model indicated that bone age and active leisure activity together explained 94.6% of the variance of the BMD. These findings indicate that BMD of adolescent synchronized swimmers tended to be unique in local regions. Furthermore, BMD in athletes was affected by the biological maturation level and physical activity in leisure time of daily life.