BACKGROUND Body-composition changes have been observed after burn injury. In particular, several studies have shown that bone mineral density (BMD) in burn patients is decreased when compared to the normal population. Little is known about the frequency, severity, or duration of these changes. The purpose of this study was to describe body-composition changes over time after burn injury. METHODS Twenty-nine burn patients participated in this study. Portable dual-energy X-ray absorptiometry (pDEXA) measuring forearm BMD, fat, and lean mass was obtained as soon as possible after admission and repeated bi-weekly until discharge and, when possible, for 2 years post-injury. The scan showing the greatest change in BMD, fat, or lean mass was compared to the baseline scan for each individual. RESULTS Although lean and fat mass did not change significantly after injury, BMD decreased significantly. The greatest change in BMD did not occur during the acute burn hospitalization, but rather 131 days after burn injury. Changes in post-burn BMD inversely correlated with % total body surface area (TBSA) and % 3rd-degree TBSA. The magnitude of change was similar between adults and children. CONCLUSIONS These results confirm earlier studies, suggesting that BMD can be negatively altered post-injury, with the greatest changes occurring after patients are discharged from the hospital. Although the clinical significance of these changes is not known, this study supports the need for long-term musculoskeletal assessments in burn patients and for further research to elucidate the mechanisms of burn-induced body-composition changes.