There is a difference in the vascular architecture of myocutaneous flaps and jejunal free flaps both available to replace resected mucosal tissue of the oral cavity after surgical treatment of oral cancer. The question in whether the mobilization of jejunal free flaps is possible without respect to the anastomized vessels in particular in secondary reconstruction procedures to achieve a bony continuity of the mandible. From 1985-1992 22 patients were operated on using microsurgically anastomized jejunal free flaps. In 7 cases a secondary mandibular reconstruction by means of microsurgically anastomized iliac crest grafts was performed. In respect of our results we recommend in cases of secondary mandibular reconstruction with mobilisation of the jejunal flap. 1. preoperative digital subtraction angiography, 2. temporary clamp of anastomized vessels with observation of the perfusion of the jejunal flap, 3. intraoperative doppler-sonography. These techniques allow a save evaluation of the vessels of the donor site prior to microvascular anastomoses for secondary bony reconstruction of the mandible.