The term mucocele is applied to define a chronic, expanding, mucosa-lined lesion of the paranasal sinus characterized by mucous retention that can be infected becoming a mucopyocele. Until recently the majority of patients with frontoethmoidal mucoceles were treated through an external approach, however, selected cases of mucoceles can be approached endoscopically, decreasing the morbidity associated to external approaches. We report the case of a frontal mucopyocele with rapid expansion and erosion of the anterior wall. Surgical aspects and postoperative follow-up are described.