Hair loss (alopecia) affects men and women of all ages and often significantly affects social and psychologic well-being. Although alopecia has several causes, a careful history, dose attention to the appearance of the hair loss, and a few simple studies can quickly narrow the potential diagnoses. Androgenetic alopecia, one of the most common forms of hair loss, usually has a specific pattern of temporal-frontal loss in men and central thinning in women. The U.S. Food and Drug Administration has approved topical minoxidil to treat men and women, with the addition of finasteride for men. Telogen effluvium is characterized by the loss of "handfuls" of hair, often following emotional or physical stressors. Alopecia areata, trichotillomania, traction alopecia, and tinea capitis have unique features on examination that aid in diagnosis. Treatment for these disorders and telogen effluvium focuses on resolution of the underlying cause.