We propose and demonstrate that the photoacoustic effect can be used for absolute determination of the optical absorption coefficient. The photoacoustic signal is measured as a function of chopping frequency and compared to the theory of the photoacoustic effect. The essential agreement of theory and experiment over a restricted frequency makes possible the determination of the optical absorption coefficient (to within 10% in a test case). Observation of a characteristic leveling off of the photoacoustic signal at low frequencies for several materials is also reported.