The fasciocutaneous flap transplanted into the oral cavity often acquires a gross appearance resembling that of intraoral mucosa. The purpose of this study was to analyze the histologic and morphological changes of the fasciocutaneous free flap in oropharyngeal reconstruction and attempt to determine the related causes. A study was done from January 2006 to February 2010. Study subjects included 67 of 239 patients who had undergone reconstructive surgery after oropharyngeal tumor resection. Histologic evaluation of biopsy specimens was also performed in 20 patients. The correlation of the morphological changes with various factors was analyzed. The histologic examination revealed that numerous histologic changes occurred although the overall structure of the skin was maintained. Analysis of the associated factors showed that the primary defect site was highly correlated with this morphological change in the intraoral flaps.Analysis of the associated factors showed that the primary defect site was highly correlated with this morphological change in the intraoral flaps. Histologic analysis reveals that fasciocutaneous free flaps maintain their feature as cutaneous skin yet undergo changes because of the characteristic oral cavity environment, which resulted in an intermediate-stage morphology.