A simple, controlled temperature irradiator which permits fabric samples to be irradiated at various air temperatures is described. Photodegradation of wool fabrics as assessed by measurement of breaking loads, tear strengths, and yellowing indexes is evaluated. A procedure is described for assessing the level of photoprotection conferred on wool by treatment with an ultraviolet absorber. See also AATA 19-415 for another study of wool degradation. -- AATA