This chapter details factors that should be considered when evaluating each patient's candidacy for deep brain stimulation (DBS). A number of factors need to be assessed in a systematic matter to determine each patient's candidacy for treatment with DBS. Parkinson's disease (PD) patients referred for surgery are at greater risk for psychotic symptoms, as they usually have relatively advanced disease. When considering a patient with essential tremor (ET) for DBS, it is important to make sure the patient meets clinical criteria for the diagnosis of ET as a first step. Determining which dystonia patients are candidates for DBS can be challenging than making this determination for patients with PD or ET. An effective method for arriving at decisions regarding the candidacy of patients for treatment with DBS is to collect the required data for each patient and then convene a conference. These details are discussed by the interdisciplinary/multidisciplinary team.