Telogen effluvium (TE) is a common clinical consequence of medication-related alopecia. The inciting cause of TE may be difficult to identify due to delays in clinically apparent hair loss. Because medication-induced TE is a nonscarring alopecia that typically is reversible, appropriate management requires identification of the underlying triggering medication and cessation of it, if possible. In part 1 of this series, we review the existing literature on medication-induced TE with a focus on systemic retinoids, antifungal agents, and psychotropic medications.