A pyocele is an indolent purulent collection within ethmoid and/or frontal sinuses with obstruction of the frontonasal duct by swollen mucosa, granulation tissue, polyps or bone produced by chronic sinusitis. The majority of mucocele and mucopyocele are located in the frontal and/or ethmoid sinuses. The authors have recently experienced a case of pyocele in the right ethmoid sinus. A 41 year-old man visited our clinic with complaints of epiphora and swelling on the right inner canthal area. CT scan revealed soft tissue mass in the right ethmoid sinus, which extended to the orbit with bony destruction of the lateral wall of the ethmoid sinus. The right eyeball was deviated to the anterior and lateral side. The pyocele was removed out sucessfully by intranasal ethmoidectomy. It contained about 5 cc of purulent discharge. The culture of pus showed negative except normal flora. The histopathological diagnosis was proved mucopyocele.