A statistical analysis was performed in patients with press-through-pack (PTP) foreign body in the esophagus encountered in the Department of Otorhinolaryngology, Tohoku University School of Medicine from 1986 to 1993. Furthermore, the radiolucency of PTP and the possibility of mucosal injury of the esophagus by PTP were examined by experimental methods. We obtained the following results: 1) The incidence of PTP foreign body in the esophagus increased in the period from 1986 to 1994 as compared with that from 1978 to 1985. 2) PTP foreign body was lodged in the following area: cricopharyngeal narrowing>bronchioaortic narrowing>hiatal narrowing. 3) Fluoroscopy with or without contrast material and flexible endoscopy were useful tools for diagnosis. 4) Direct esophagoscopy revealed mucosal erosion, hematoma, edema and intact mucosa in 14, 3, 3, and 6 patients respectively. 5) The period of hospitalization was longer in patients with mucosal erosion than in those with intact mucosa. 6) The base of PTP made of aluminium could be detected as a radiopaque material by lateral projections, suggesting that PTP foreign bodies require roentgenograms made pararell to the base of PTP. 7) Histological study indicated that traumatic lesions in the extracted esophagus manually produced by the sharp corner of PTP were present in the mucosal layer and partially in the submucosal layer, suggesting that esophageal perforation by PTP was generated by additional factors such as secondary infection and iatrogenic trauma induced by esophagoscopy.