Transcranial magnetic stimulation (TMS) is a non-invasive modality that uses an electromagnetic field to stimulate specific areas of the brain’s cortical surface. Compared to existing psychopharmacological interventions, TMS is associated with fewer adverse effects and received FDA approval for treatment-resistant depression in 2008 and has subsequently been cleared for treating many other conditions including obsessive compulsive disorder (OCD), smoking cessation, migraine, anxious depression, and neuropathic pain. Given the rate of progress and the tremendous gains achieved in the field of neuromodulation thus far, there is little doubt that the future of TMS holds great promise for the treatment of neuropsychiatric illnesses. Despite the recent growth of knowledge involving the application of TMS in neurophysiologic research and interventional psychiatry, much remains to be known in the safety and efficacy of TMS, particularly in specific populations such as the elderly and those with neurological conditions. While some research on the use of TMS in older populations have yielded promising results, many clinical trials continue to exclude this population because of insufficient evidence regarding safety and efficacy. This further limits the clinical evidence when treating older individuals and those with neurological conditions. Attention to this clinical conundrum is warranted. This chapter focuses on the evidence for using TMS when treating older patients and patients with neurological conditions.