Loss of eyebrow hair may come to the attention of the dermatologist as a presenting complaint or as an unexpected finding on routine physical examination. Because eyebrows serve important cosmetic and social roles, their loss can be quite distressing to patients. While eyebrow loss may be an isolated finding of no medical consequence, it may also be an initial manifestation of a systemic condition. Loss of eyebrows has numerous causes including primary dermatoses, endocrinopathies, autoimmune conditions, infections, neoplasms, trauma, exogenous agents, and genetic diseases. We present a systemic review of eyebrow loss, including an algorithm that can be used to direct the work-up of patients presenting with this condition.