Linear elastic three-dimensional (3-D) finite element (FE) analyses of a concrete gravity dam modelled both with and without reservoir effects were conducted to determine natural frequencies and mode shapes of the dam. These analyses were compared to experimental results of prototype vibration tests before and after reservoir impoundment. Mode shape comparisons between prototype and FE model results were evaluated using a modal assurance criterion. Favorable correlations between experimental and FE mode shapes were computed for the dam without reservoir effects, indicating that a reasonable 3-D FE model was developed. Analytical estimates of natural frequencies were higher than measured experimentally.