The objective of the present study was to assess the feasibility of using endogenous fluorescence in intraoperative prediction of skin flap necrosis. The investigation was carried out in 10 Sprague-Dawley rats in which proximally based over-dimensioned random pattern skin flaps were dissected on the back and thereafter fixed into position. Immediately after surgery on each rat, synchronous fluorescence spectra (Deltalambda=90 nm) from five parts of the skin flap surface were measured. The presence of necrosis was evaluated on postoperative day 7. In flap parts designated as necrotic (n=18), a significantly lower (P<0.001) fluorescent signal from the nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) bands (360-380 and 440-460 nm, respectively) was detected in comparison with the vital parts (n=32) (for FAD:1767+/-39 versus 2579+/-65 auxiliary units [A.U]. and for NADH:11724+/-340 versus 16810+/-473 A.U.). The results suggested a close relationship between the fluorescent signals from the FAD and NADH bands on one side and flap necrosis or survival on the other side. Thus, the use of fluorescence spectroscopy may be considered as a valuable noninvasive tool for the prediction of skin flap necrosis.