OBJECTIVE: To quantify the increase in the likelihood of a fall injury and medical costs of treating fall injuries among elderly individuals with select mental health (MH), substance abuse (SA), and cognitive disorders compared with the general elderly population. METHODS: The authors used a random sample (N = 601,922) of claimants in the 2001 Medicare fee-for-service 5% Standard Analytic File. Using logistic regressions, the authors estimated the odds of sustaining a medically attended fall injury as a function of each MH, cognitive, and SA condition and select demographic characteristics. The authors also used an ordinary least squares regression model to compare the increase in costs associated with fall injuries for those with MH/SA conditions compared to those without MH/SA conditions. RESULTS: The odds of a fall injury are between 1.5 and 4.5 times greater for those with MH and SA conditions among both elderly men and women. Odds of a fall injury among elderly individuals with Alzheimer disease and other dementias are at least three times greater, and the differential increases with age. The increases in cost resulting from a fall injury are greater among both elderly men and women with MH conditions and Alzheimer disease and other dementias and among elderly women with SA conditions. CONCLUSION: The substantial burden of fall injuries among the elderly with MH/SA conditions suggests the need to direct fall prevention and mitigation strategies specifically toward this vulnerable population.