Individuals with intellectual disability (ID) or Down syndrome (DS) may be at greater risk of osteoporosis. The purpose of this study was to compare bone mineral density (BMD) of DS, ID, and non-intellectually disabled (NID) populations. In each group, 33 participants between the ages of 28 and 60 years were compared. BMD was measured with dual-energy x-ray absorptiometry (DXA) scans. BMD ("p" < 0.0001) between all groups was significantly different. Participants with DS had significantly lower BMD compared to NID participants. Individuals with ID had significantly lower BMD compared to NID subjects. Participants with DS had the lowest BMD of all groups. DS subjects display a greater risk for osteoporosis than ID subjects or control populations.