Partial-thickness rotator cuff tears are not a single entity; rather, they represent a spectrum of disease states. Although often asymptomatic, they can be significantly disabling. Overhead throwing athletes with partial-thickness rotator cuff tears differ with respect to etiology, goals, and treatment from older, nonathlete patients with degenerative tears. Pathogenesis of degenerative partial-thickness tears is multifactorial, with evidence of intrinsic and extrinsic factors playing key roles. Diagnosis of partial-thickness rotator cuff tears should be based on the patient's symptoms together with magnetic resonance imaging studies. Conservative treatment is successful in most patients. Surgery generally is considered for patients with symptoms of sufficient duration and intensity. The role of acromioplasty has not been clearly delineated, but it should be considered when there is evidence of extrinsic causation for the partial-thickness rotator cuff tear.