Flow of a Newtonian liquid film and the supporting liquid with a longitudinal wave disturbance, which is imparted to the liquid film by means of a sinusoidally oscillating barrier, is numerically simulated in a rectangular trough. The effects of surface dilatational viscosity and elasticity of the liquid film on amplitudes and time lags of tracer particles deposited on the liquid film are investigated. A comparison between the present theoretical results and predictions based on a linear oscillation theory by Maru and Wasan (1979 b) indicates that the oscillation of films cannot be expressed by the simple linear theory, and that the measurement of surface dilatational viscosity by the longitudinal wave technique needs a more exact analytical method, Experiments on the oscillation in a castor oil-water system were carried out. Analysis of the experimental results based on the present theory shows that the surface dilatational viscosity of castor oil is Newtonian.