A skin island carried by pectoralis major muscle has been used to reconstruct an intraoral defect created after resection of a tumor. To our knowledge, what happens to the skin after its mobilization from the chest wall into the mouth has not been documented. To answer this, a wedge biopsy of the intraoral skin island on the pectoralis muscle was performed in 14 patients under local anesthesia. The skin biopsy specimen was subjected to scanning electron microscopic and histologic examination. The interval between the reconstructive surgery and the biopsy ranged from ten to 66 months (mean, 32 months). The results revealed desquamation of the epidermis and loss of appendages. The degree of desquamation was maximal when the skin island was used to replace the whole of the floor of the mouth and least when it was used for the lateral portion.