High-pressure luminescence studies have been made on a polymer with a polystyrene base but with every seventh styrene converted to benzophenone (BP). The polymer was studied neat (PVBS) and in a 10% solution in polystyrene (PVBS-PS). As for BP dissolved in polymers, both photophysical and photochemical effects are observed originating from the triplet state (T 1 ). For PVBS, in addition to the phosphorescence from the monomer, an emission at lower energy occurs which we identify as an excimer and some emission at higher energy identified as delayed fluorescence. In PVBS-PS there is little or no excimer but more intense delayed fluorescence. For PVBS the strongest photophysical effect occurs in the first few kilobar where the excimer intensity increases by a factor of 3-4 at the expense of the monomer phosphorescence. At higher pressure both emissions decrease. For PVBS-PS the phosphorescence (measured on its lowenergy side) shows first a modest increase and then a decrease, analogous to the behavior of BP dissolved in polymers. The delayed fluorescence decreases significantly with increasing pressure. The major effect of irradiation is the dramatic growth of a new emission 4000 cm -1 below the monomer phosphorescence. We attribute this to an emitting photo product much like that observed for BP dissolved in polymers but shifted strongly to lower energy. This occurs in both PVBS and PVBS-PS. The intensity of this emission decreases with increasing pressure. A second effect of irradiation is the strong decrease in the delayed fluorescence, which we attribute to the decreased availability the original phosphorescence for T 1 f S 1 back-feeding.