Early recognition of threatened free-flap failure is paramount to flap salvage. A noninvasive, reproducible, sensitive monitoring tool would be a useful adjunct to clinical examination. The purpose of this study was to examine outcomes using a near-infrared spectroscopy (NIRS) tissue oximeter for postoperative flap monitoring. A total of 128 free flaps were performed in 113 patients over a 3 year period. The patients were divided into 2 cohorts: conventional monitoring (group 1) and conventional monitoring plus NIRS oximetry (group 2). Overall flap survival was 90.6% in group 1 and 98.7% in group 2 (P = 0.05). Overall survival of threatened flaps was 0% (0/5) in the conventional group and 87.5% (6/7) in the oximeter group, P = 0.005. Salvage of operated flaps was significantly improved in group 2: 0% (0/4) in group 1 versus 100% (3/3) in group 2, P = 0.03. The sensitivity, specificity, and predictive values for detecting threatened flap loss were 100%. The NIRS tissue oximeter is a highly reliable, sensitive, and specific, noninvasive method for postoperative free tissue transfer monitoring.