Clinical assessment of the perfusion of the musculocutaneous portion of composite iliac crest free flaps was compared to 99mTc-diphosphonate (HDP) uptake in 14 patients who underwent primary oromandibular reconstruction after ablative cancer surgery. Bone scanning was performed on average at the 9-10th postoperative day (range 4-48) 3 h after intravenous injection of 550 MBq 99mTc-HDP. Eleven patients showed complete concordance between 99mTc-HDP uptake and soft-tissue status. Two patients showed uptake and viable muscle in spite of necrotic skin. One patient had a viable musculocutaneous flap but a photopenic defect in the bone graft; 6 months later, a small corresponding part of the bone was sequestrated. In this study, bone scanning and clinical assessment of muscle perfusion were 100% accurate in predicting viability of bone grafts. Skin viability was a less reliable parameter. It is concluded that bone scanning is not indicated as a routine investigation for revascularized iliac crest flaps and that clinical assessment of muscle perfusion is a reliable monitor of the early function of such flaps.