Although older monoamine oxidase inhibitors (MAOIs) are effective in the treatment of depressive disorders, they are underutilized in clinical practice due to main concerns about interaction with tyramine-containing food, and side effects. Efforts to address these safety issues led to the development of a transdermal formulation of selegiline, called selegiline transdermal system (STS). STS has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of major depression. Transdermal administration of selegiline bypasses gastrointestinal absorption and first-pass metabolism. Therefore, STS permits inhibition of monoamine oxidase (MAO)-A and MAO-B enzymes in the brain while preserving the activity of MAO-A in the gastrointestinal system, thereby minimizing the risk of possible interactions with tyramine-rich foods. Tyramine challenge tests have confirmed that dietary modifications are not required with the 6 mg STS. The FDA has required dietary modifications with the 9 mg and 12 mg STS. Compared to oral administration, transdermal selegiline leads to sustained (minimal peak-trough fluctuations) plasma concentrations of the parent compound, increasing the amount of drug delivered to the brain. The efficacy of STS has been established in several short-term and one long-term randomized controlled trials. In clinical trials, application site reactions and insomnia were observed more frequently with STS than placebo. Rates of orthostatic hypotension, sexual dysfunction and weight gain were comparable between STS and placebo. STS is a new generation of MAOI with superior safety profile to older MAOIs. It increases the pharmacological options available to treat depressive disorders and may benefit patients with major depression with atypical features and resistant depression. It is important for health-care professionals to be informed about the properties of STS.