Photoacoustic Fourier transform infrared spectroscopy has been used to characterize naturally and artificially aged fibers of cotton. Naturally aged cotton fibers from archaeological sites in the southwest United States exhibited a family of pronounced absorption bands in the C=O stretch region of the infrared spectrum (1600-1750 cm^-1) not found in fibers from new cotton cloth. New cotton fibers artificially aged at Ü0 160°C in air exhibited strikingly similar spectral features, along with a severe loss of fiber tensile strength. Cotton artificially aged at 190°C in a nitrogen atmosphere exhibited a similar loss in fiber tensile strength, but without developing new C=O bands. This suggests that the decrease in cotton fiber tensile strength may occur via several mechanisms, or may be only coincidentally associated with the development of C=O absorption bands. Nevertheless, photoacoustic spectroscopy may be used as a rapid, sensitive, and nondestructive method to predict the extent of oxidative degradation in naturally aged samples of cotton textiles. -- AATA