Polystyrene and pigmented polystyrene films with a loading of either 3% phthalo blue (blue), 3% of phthalo green (green) or 1·5% of 2, 3, 10, 11, 18, 19, 26, 27-octakis(dodecyloxy)-phthalocyanine (DD green) were exposed to simulated solar radiation ranging from 250 to 1100 nm inside a vacuum chamber at a pressure of approximately 1·0 × 10-6 torr. Changes in the fluorescence spectra of the photodegraded samples were examined. Gel permeation chromatography (GPC) analysis indicated that all the photoirradiated samples had a higher molecular weight than their unexposed counterparts. The percentage increase in molecular weight of the polymer varied with the type of pigment. In general, the increase in the weight average molecular weight of phthalocyanine pigmented polystyrene was less than the unpigmented counterpart, while phthalocyanine pigments produced more cross-linked insoluble material. © 1995.