A thin‐film resonance technique is described for measuring the dispersion and absorption of acoustic waves in lossy liquids from 0.5 to 2.2 GHz. The method uses Bragg scattering of laser light to measure the incident and reflected acoustic power from a 4.2‐μ liquid film formed between two sapphire rods. It is shown how the velocity and absorption are calculated from the measured acoustic reflection coefficient. The technique is used to study the two Dow Corning resins 276‐V2 and 276‐V9, both of which are found dispersionless within experimental error. The absorption per wavelength initially decreases with frequency for both resins; for resin V9, however, the absorption shows an increase at the higher frequencies. The results obtained are interpreted in terms of relaxational processes.