Hair loss, or alopecia, may occur as a primary skin disorder or because of an underlying health problem. It may be upsetting to patients, particularly adolescents who are experiencing physical, emotional, and psychological transitions. Understanding the impact of alopecia is important for care providers who see adolescents.The most common forms of alopecia in adolescence are telogen effluvium, androgenetic alopecia, and alopecia areata. Telogen effluvium may present suddenly or insidiously secondary to a variety of triggers. Androgenetic alopecia may begin in adolescence, and topical minoxidil is effective at retarding further hair loss. It may be a sign of underlying androgen excess, particularly polycystic ovary syndrome in women. Alopecia areata is less common, but may be distressing, especially if hair loss is extensive. Because treatments for alopecia are not curative, helping affected patients cope by offering support and nonpharmacologic techniques to help appear more like their peers should be part of care.Physicians need to be skilled in evaluating the most common forms of alopecia presenting in adolescence and should be aware of potential treatments, including the value of psychosocial support.