We report on a healthy 26-year-old male who had an exercise-induced pulmonary hemorrhage (EIPH) within 24 hours of running a marathon. There were no symptoms, abnormalities on exam, or radiographic infiltrates. He routinely participated in bronchoscopy research and the EIPH was evident on gross inspection of bronchoalveolar lavage fluid, examination of the cytospin, and measurement of hemoglobin, iron, and ferritin concentrations. EIPH in humans may occur without any evidence on clinical presentation; its incidence may be far greater than currently suspected.