The need to cover the exposed periostium has meant that a number of materials including mucosal and skin grafts are regarded as suitable for grafting in oral and maxillofacial surgery. To circumvent the disadvantages of other materials such as skin, biological membranes have been suggested as options, including fetal membrane. The objective of the present study was to evaluate the clinical efficacy of amnion as a graft material for vestibuloplasty, to increase the depth of the sulcus for complete rehabilitation with dentures in 10 patients with a follow up period of 3 months. Ten patients with deficient depth of the mandibular vestibular sulcus who were referred from the Department of Prosthodontics were listed for mandibular labial vestibuloplasty using Clark's technique followed by grafting with amnion over the denuded periostium. The vestibular depth was evaluated at the end of the 1st week, 2nd week, 4th week, and 3rd month postoperatively, and compared with the preoperative vestibular depth. We had no cases of graft necrosis either complete or partial. However, the reduction in the depth of the labial vestibule ranged from 17% to 50% after 3 months' follow up. A mean (SD) labial vestibular depth of 13.3 (1.8)mm was achieved immediately postoperatively, and 10.0 (3.1)mm at 3 months' follow up. We conclude that grafts of amniotic membrane are viable and reliable for covering of the raw surface, prevent secondary contraction after vestibuloplasty, and maintain the postoperative vestibular depth.