A patient complaining of chronic dull pain in the right maxillary area showed slight haziness and small ovoid radiopacity in the right antrum, which was not extended into the choanal area in radiographic views. At operation, lots of mucoid fluid admixed myxoid soft tissues was discharged and the polypoid mucosal tissues were removed. In histological examination, the removed tissues showed a polyp by the overgrowth of dermal connective tissues exhibiting severe myxoid degeneration. Throughout the entire specimen, the inflammatory reaction was diffuse but not so remarkable to produce the mucosal thickening and necrosis. The polypoid tissues were diffusely infiltrated with neutrophiles and plasma cells, but few eosinophils, resulted in the extensive myxoid degeneration together with severe vascular degeneration. Therefore, we suggest that the antral polyp is basically different in its pathogenesis and prognosis from the common maxillary sinusitis of odontogenic origin, thus the antral polyp should be carefully diagnosed when the inflamed antral lesion is recurred and diffusely degenerative with myxoid changes.