OBJECTIVES: One-third of Medicare beneficiaries <65, who are deemed eligible for Social Security Disability Insurance, are disabled due to a mental disorder. But psychiatric services research targeting this population is limited. This study estimated annual trends in and identified factors associated with psychotropic prescription utilization among disabled Medicare beneficiaries <65. METHODS: This serial cross-sectional study used 2002-2009 Medicare Current Beneficiary Survey data. Nationally representative community-dwelling Medicare beneficiaries <65 were included (n=10,384 person-years, weighted n=30,086,849 person-years). Psychotropic prescription utilization included self-reported antidepressants, antipsychotics, stimulants, mood stabilizers, anxiolytics, hypnotics, and antimanic prescription use. Weighted annual trends in psychotropic prescription utilization were estimated. Repeated person-year data using generalized estimating equations multivariable models were used to identify factors associated with psychotropic prescription utilization. RESULTS: Annual prevalence of any psychotropic prescription utilization among disabled Medicare beneficiaries <65 increased from 53.4% to 57.9% in 2002-2009, but the trend was not statistically significant (P=0.36). Antidepressants (35.09%), hypnotics (20.16%), and anxiolytics (17.31%) were the top three therapeutic classes used in 2009. No significant trend in utilization was observed for any individual therapeutic classes. Multivariable results showed that beneficiaries <65 who were female, white, divorced, Medicare-Medicaid dual eligible, with higher education and poorer health status, smoking, and having chronic and psychiatric conditions were more likely to use any psychotropic prescriptions (all P<0.05). Female and white beneficiaries were more likely to use all psychotropic therapeutic classes except for antipsychotics (females only) and stimulants/antimanics (whites only). Beneficiaries with poorer health status and chronic conditions were more likely to use antidepressants, anxiolytics, and hypnotics. Medicare-Medicaid dual enrollees were more likely to use antipsychotics (all P<0.05). CONCLUSIONS: Psychotropic prescription utilization is prevalent among disabled Medicare beneficiaries <65. Patterns of use vary by psychotropic therapeutic class. Future research needs to evaluate psychotropic prescription access and quality of use among this vulnerable population.