Chemiluminescence (CL) is a straightforward method for studying the free radical degradation of organic and biological materials. A simple modification to a commercial thermal CL instrument and an effective experimental protocol allows the study of photoinduced chemiluminescence (PICL) emission. PICL originates from the reactions of macroperoxy radical intermediates formed during the autoxidation chain reaction. We have applied the PICL technique to study the photooxidation of polymer films and coatings, fibrous webs such as textile fabrics or paper, and powdered samples. Oxygen permeability appears to be a key factor affecting the intensity of PICL emission from polymer films.