The technique of excimer fluorescence has been employed to study the orientational structure of poly (methyl methacrylate) (PMMA). The PMMA films used contain a small amount of naphthalene-labeled PMMA, and were uniaxially stretched to various elongation at 80 degrees C. The results show that the fluorescence intensity ratio of excimer to monomer, I-E/I-M, increases with the elongation ratio. The increase of excimer forming sites in the system after drawing is attributed to the orientation of both the chain segments and side groups along the drawing direction. The orientation leads to highly dense packing of the PMMA molecules. The conclusion drawn from excimer fluorescence is in agreement with those from other techniques.