To circumvent the disadvantages of extraoral skin within the oral cavity and to cover mucosal defects by mucosa, we successfully prelaminated the radial forearm flap by insertion of buccal mucosa in ten patients. In a first-step operation, free grafts of buccal mucosa were fixed to the forearm fascia and covered with an alloplastic sheet, separating the mucosa grafts and the dissected fascia between and around the grafts from the overlaying subcutaneous tissue. The dimension of the alloplastic sheet in the subcutaneous pocket was chosen according to the size of the desired flap. Underneath the alloplastic sheet, the mucosal grafts merged and the mucosal surface increased by advancing of epithelial cells under in vivo culture conditions. After two months, mucosal prelamination of the distal radial forearm fascia had led to thin, pliable and resistant fasciomucosal flaps with a mucosal surface up to 7×4 cm, allowing physiological intraoral reconstruction. The preservation of skin and subcutaneous tissue of the forearm also enabled primary wound closure, reducing donor-site morbidity.