The horns of a 13-yr-old Dall sheep ram (Ovis dalli dalli) from the Sheep Mountain herd in Kluane National Park (Yukon, Canada) had unique characteristics. The right horn was 1,127 mm long, while the left horn was only 861 mm long and compressed and distorted at its base. The reduced growth of the left horn was due to chronic epidermitis and osteomyelitis of the cornual process, which began when the ram was 5 yr of age.