A fluorescence method using labeled chromophores to study the curing kinetics of a polyurethane (PU) system was developed. A PU system based on fluorescent-labeled hexamethylene diisocyanate and a polyol (polyether/polyester) was cured at different temperatures (25, 40, 50, and 65degreesC). The fluorescent response from the 5-dimethylaminonaphtalene-1-(N-2-aminoethyl)sulfonamide and 4-methacryloylamino-4'-nitrostilbene moieties chemically bonded to the PU system was monitored as a function of the curing time. With the fluorescence data, it was possible to model the kinetics of the curing process. Methods based on the fluorescence intensity ratio and the first moment of the fluorescent band emission were applied to determine the degree of curing of the PU system. In addition, it was possible to calculate an apparent activation energy for the curing process, and a value of 17 kJ/mol was obtained.