The present study aimed to determine the effect of 20 weeks of whole body vibration (WBV) on the body composition of adolescents with Down syndrome (DS). Thirty adolescent with DS were divided into two groups: control and WBV. Whole body, upper and lower limbs body fat and lean body mass were measured with dual energy X-ray absorptiometry (DXA) before and after 20 weeks of WBV training. Repeated measures of ANOVA adjusting by height, weight and Tanner stage were used to analyze possible group by time interactions on body composition. The adjusted percentages of change in body composition were also compared between control and WBV groups. No group by time interactions were found for any variable, but the WBV group showed a higher reduction in body fat at the upper limbs (p less than 0.05), and a tendency toward higher percent increase in whole body lean body mass. Overall, a 20-week WBV training is not enough by itself for increasing lean body mass in adolescents with DS, but it might be helpful for improving body composition in this population. Its relationship with health and autonomy enhances the importance of these results. (Contains 2 figures and 3 tables.)