Many otologists use tissue grafts for obtaining successful healing of a perforated tympanic membrane and some suggestions have been made on the role played by the graft in the healing process without adequate experimental evidences. Moreover, fundamental data on the wound healing process of the grafted tympanic membrane according to the grafting methods are extremely scarce. Human amniotic membrane is a versatile wound dressing and was used for tympanic graft by some otologists without adequate histopathological study. The object of the present study is to examine the host reaction of transplanted human amniotic membrane and differences between the effects of the ONLAY graft and the UNDERLAY graft on the healing process of the tympanic membrane and the fate of the graft itselt. Human amniotic membrane was implanted in cats' muscles and grafted on perforated tympanic membranes by both onlay and underlay grafting methods. Results obtained were as follows : 1) Transplanted human amniotic membrane was not rejected in the muscles and tympanic membranes of the animals. Although mild inflammatory reaction was accompanied, progressive disintegration and organization of the amniotic membrane was noticed. 2) Repairing sequences of each layers of the healing tympanic membrane showed : in CONTROL group the perforation was obliterated with squamous epithelium followed by connective tissue and mucosa ; in ONLAY group, with connective tissue and mucosa followed by squamous epithelium ; in UNDERLAY group, with connective and squamous epithelium followed by mucosa. 3) Relationships of the graft with each layers of the healing tympanic membrane showed : in ONLAY group squamous epithelium migrated between the graft and connective tissue ; in UNDERLAY group connective tissue migrated lateral to the graft, mucosa medial to it. 4) The fate of the graft showed : in ONLAY grafting the graft was shed off as the tympanic membrane healed ; in UNDERLAY grafting the graft remained in the healed tympanic membrane. 5) Histoacryl used in ONLAY grafting showed no significant toxic reaction on the tympanic membrane. Gelfoam used in UNDERLAY grafting induced mild or moderate tissue reactions in the middle ear cavity and seemed to disturb mucosal or epithelial growth. Based on the results it was concluded that the grafted amniotic membrane played the scaffold role successfully in the healing process of the perforated tympanic membrane in early stage which may prevent squamous epithelial ingrowth into middle ear and possible infection, and it was thought that early grafting would help the healing process of a perforated tympanic membrane.