In oro-maxillofacial malignancies, new therapeutic approaches are placing changing demands on the diverse diagnostic modalities. In contradistinction to mandibular reconstruction of former years, the transplants (microvascular anastomosed pedicled flaps, "flaps") now consist of one or more arteries feeding a soft tissue component attached to a piece of bone suitably fitted to fill the defect. We addressed the diagnostic value of technetium-99m tetrofosmin scintigraphy in differentiating between viability and non-viability of the soft tissue portion of flaps in the immediate postoperative assessment. A total of 60 patients who had received flaps for reconstruction of the mandible after partial resection were investigated with (99m)Tc-tetrofosmin 3-5 days after surgery. Scintigraphy consisted of (a) radionuclide angiography, (b) static planar imaging in four projections starting at 10 min post injection, and (c) single-photon emission tomography (SPET) performed immediately after the planar imaging. Normal perfusion associated with no defects throughout the soft tissue portion of the transplant was observed in 46/60 patients. This scintigraphic pattern was identical to viability and normal postoperative follow-up. Hypoperfusion and small defects on planar and SPET images indicated viability and uncomplicated postoperative healing in 6/60 patients, but non-viability/inadequate healing of the flap in 4/60 patients. Absence of perfusion combined with a large defect on static planar and SPET images definitively showed the non-viability of the flap (4/60 patients). It is concluded that (99m)Tc-tetrofosmin scintigraphy is a sensitive diagnostic tool for the immediate postoperative assessment of the viability and the adequacy of implantation of the soft tissue portion of flaps. Therefore tetrofosmin scintigraphy is an important modality in order (a) to define the optimal therapeutic regimen in the immediate postoperative period and (b) to provide better prognosis.