The photooxidative degradation of acrylic fibers was investigated with two different fiber-spinning processes, that is, dry spinning and wet spinning. Several analytical methods were used in this study: viscometry, X-ray diffraction, Fourier transform infrared spectroscopy, optical measurements, and mechanical testing. Viscometry was used to determine the molecular weight as a monitoring factor for degradation. X-ray diagrams showed lower changes in the crystallinity of wet-spun fibers during a weathering process by irradiation. The results from mechanical testing indicated that the tenacity of dry-spun fibers had less deterioration than that of wet-spun fibers. Degraded wet-spun and dry-spun fibers showed similar trends in optical and spectroscopy analysis. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 945-952, 2009