Polymeric nonlinear optical waveguides of a copolymer of 4-(N'-2-methacroyloxyethyl-N-methyl-amino)-4'-nitrostilbene and methyl methacrylate were tested for optical power handling capability at near-infrared wavelengths. When exposed to about 5 X 10(5) W/cm2 optical power density at 1325 nm wavelength laser light, the waveguide showed a rapid decay of optical transmission on the order of about 3 dB/h. Operation of the waveguides in an oxygen-free environment significantly reduced the decay rate to greater than 0.25 dB/h. The decay was a result of spatially inhomogeneous change of refractive index distributed along the length of the waveguides. Micrographs showing the photoinduced local variations of refractive index and the resulting loss of optical confinement of the waveguides are presented.