OBJECTIVES:  To identify characteristics associated with specialty medication use by employing a large, nationally representative sample of patients using specialty medications for their chronic conditions in the U.S. METHODS:  This study used Medical Expenditure Panel Survey (MEPS) data from 2000 through 2013. Among the MEPS respondents aged 18 or older who received at least one medication during the years 2000 through 2013, those who used any specialty pharmaceuticals were considered as specialty medication users (SMUs). Accordingly, adults 18 or older who used only pharmaceuticals other than specialty medications were considered traditional medication users (TMUs). Those who used not only specialty medications but also traditional medications concurrently were labeled as both medication users (BMUs). Andersen’s Health Services Utilization model was used to identify potential factors related to specialty medication use. Associations between the variables identified by Andersen’s model and specialty medication use were analyzed using logistic regression in a hierarchical fashion. Sampling weights were considered and standard errors were adjusted to account for the complex survey design. RESULTS:  A fully adjusted model suggested that older adults or individuals using mail order services were more likely to use specialty medications regardless of whether they used traditional medications concurrently. Behaviors of using specialty medication(s) were positively associated with married and active working status and negatively associated with middle or high income and having a usual source of care (visiting a doctor’s office, clinic, or health center they usually go when sick) when comparing TMUs and SMUs. In addition, when comparing TMUs and BMUs, behaviors of using specialty medication(s) were positively associated with female gender, having drug insurance, worse health state and more comorbidities and negatively associated with other race/ethnicity (not Caucasian/African American). CONCLUSIONS:  This study identified characteristics of patients using specialty medication(s). Some sociodemographic, economic, and clinical factors were related to specialty medication use among U.S. adults.