Prevalence of overweight among the general population has been reported to be 33% for males and 36% for females. We undertook this study to establish overweight prevalence data in a cohort with Down syndrome and to stratify the incidence of overweight by living arrangement. We measured Body Mass Index (BMI) in 283 persons with Down syndrome and found a higher prevalence of overweight in this group compared to the general population. Individuals with Down syndrome living in a family setting had a higher incidence of overweight than did those living in a group home setting. Overweight prevalence among persons with Down syndrome should be considered a major public health concern that warrants further attention from researchers, practitioners, family members, and individuals with Down syndrome.