We report efficient room temperature phosphorescence induced by pressure (PIP) and/or by continuous light irradiation (light-induced phosphorescence (LIP)) in two ketones : benzophenone (BP) and its p-dimethylamino-substituted (Michler’s ketone (MK)) both dissolved in solid poly(ethyl methacrylate) (PEMA). Under pressure both BP and MK reveal a remarkable growth of the phosphorescence intensity : 2 orders of magnitude (within 5 kbar) and 1 order of magnitude (within 50 kbar) respectively for MK and BP. For MK, above 5 kbar the phosphorescence intensity significantly decreases, but for BP the decrease is negligible even above 50 kbar. A model based on the increase of the amount of pi,pi* character in the predominately n,pi* tripler state with increasing pressure is proposed to account for the observed features of the PIP. The LIP occurs only at pressures below the maximum in the PIP. With prolonged irradiation, the overall shape of the phosphorescence intensity curve versus time depends on pressure, exciting light intensity, and concentration. A tentative explanation of the LIP effect is given that assumes a creation of the phosphorescent photoproduct via the hydrogen abstraction reaction.