This paper presents an analytical method to study free and forced longitudinal vibrations of embankment dams. Both shear and dilatational deformations are taken into account, and the dam is modeled as a linear homogeneous prism with a wedge-shape cross section, bounded by two vertical (abutment) and one horizontal (riverbed) planes. Numerical results demonstrate the effect of the length and height of the dam on its natural frequencies and its modal displacement and strain shapes. It is shown that shear deformations are more important in relatively long dams, whereas the opposite is true with dams built in narrow canyons. The method is evaluted through two case histories involving an earthfill and a rockfill dam. Close agreement exists between predicted and observed natural frequencies, but the distribution of peak accelerations within the dam is badly predicted.