OBJECTIVE To evaluate femoral head bone viability following free vascularized fibular grafting (FVFG) for osteonecrosis using SPECT/CT imaging. METHODS Ten hips (9 patients) with osteonecrosis of the femoral head (ONFH) undergoing FVFG were prospectively enrolled. Four cases showed ARCO stage II, while six showed ARCO stage III. The mean age at surgery was 15.7 years (range, 13-22 years). Hip Harris Score (HHS) was measured pre- and post-operative. Bone scintigraphy with SPECT/CT was performed at 2 weeks and 6 months following surgery. RESULTS Mean follow-up was 4.0 years (range, 2-5.9 years). Mean HHS increased from 37.2 to 92.3. SPECT/CT findings revealed a progressive increase of femoral head uptake in all cases, suggesting subchondral graft bone viability. No progressive deformation of the femoral head was evidenced in radiographic evaluation at final follow-up. CONCLUSIONS This study demonstrates FVFG's capacity for revitalizing femoral head subchondral bone grafting in patients with ONFH, surgically treated following Urbaniak's technique. © 2015 Wiley Periodicals, Inc. Microsurgery 36:573-577, 2016.