The results of dynamic non-linear two-dimensional finite element analyses of the Long Valley Dam in the Mammoth Lake area of California subjected to a real measured earthquake are presented. A simple elastic perfectly plastic constitutive soil model is used to describe the stress-strain response of the soil and Rayleigh damping (i.e. viscous damping) is applied to account for the lack of hysteretic damping. The effect of the initial stress condition and the Rayleigh damping ratio are discussed, and the results of the analysis are compared to the measured response of the dam and to results presented by previous researchers. Good agreement is obtained in the up/downstream direction, but as experienced by previous researchers, the correct vertical frequency range is not achieved. The limitations of using viscous damping combined with simple constitutive models when studying the dynamic behaviour of real earth dams are shown. Copyright © 1996 Elsevier Science Ltd.