The fluorescence spectra of pyrene and Prodan in hexane-methylethylketone solutions, which are models of polyethylene degradation, were investigated to develop a method for understanding the degradation of polymer materials. The fluorescence properties of pyrene and Prodan were highly sensitive to the polarity of the solutions. The fluorescence intensity ratios, I-384/I-373 for pyrene and I-380/I-420 for Prodan, were useful indexes for investigating the local chemical environment. These fluorescence indexes may be more than 10 times sensitive to the conventional carbonyl index by infrared absorption. This fluorescence probe method will find further application in the evaluation of polymer degradation.