Rocky Mountain elk (Cervus elaphus nelsoni) bearing malformed antlers have been observed in northern Arizona during the last 10 years. We collected measurements from 28 skulls of bulls bearing abnormal antlers from the Hualapai Indian Reservation in northwestern Arizona. Most abnormalities were unilateral. Deformed antlers were smaller and had fewer points than normal ones, and originated from deformed pedicles. The abnormal pedicles tended to be larger, and varied in orientation and location relative to normal pedicles. Some males lacked pedicles on 1 side, and the deformed antlers originated directly from the frontal bones. Similar antler and pedicle abnormalities have been documented in other elk populations in northern Arizona. The appearance of the abnormal pedicles was consistent with fracture and subsequent repair of the bones. Such damage might be incurred during sparring among males, and multiple factors might predispose the pedicles to injury.