A case of extracranial espontaneous pneumatocele, diagnosed and operated on with good results is reported. The authors coment about the physiopathology, enfasizing as principal cause the alteration in the development of the petroscamous fissure, that makes the air going from them to the Eustaquian tubes reaching the median ear and the mastoid cells wich will suffer a constant pressure resulting in this way a progressive increase of the pressure followed by rupture and propagation of the air to the subaponeurotic space. A review of cases previously described has been made.