Transtympanic facial nerve paralysis resulting from a penetrating injury through the external auditory canal is a rare occurrence. The common mechanism of paralysis is direct fracture or penetration of the fallopian canal. Slag injuries of the ear caused by hot sparks or molten metal are well known to otolaryngologists because they often result in chronic tympanic membrane perforations and chronic otorrhea. We have encountered two unusual cases of transtympanic slag injury to the ear that resulted in facial nerve injury. In one patient, a significant inner ear injury also occurred. A pathophysiologic mechanism of thermal injury is proposed, and the use of ear protection in welders is discussed.