Stahl's ear is an anomaly of the external ear that is characterised by a third crux in the antihelix. Its aetiology is unknown. We report 5 patients with Stahl's ear, and describe the anatomy, particularly the musculature. We identified the position of the transverse muscle of the ear as being abnormal, and this can take 2 forms: an abnormal insertion of the entire muscle, or an abnormal insertion of the superior head of the muscle.