The modeling and dynamic analysis of concrete arch dams, the impounded water and foundation rock, is an important step in the earthquake safety evaluation of such systems. A linear earthquake analysis assuming an arch dam is an elastic monolithic structure usually shows large tensile stresses that exceed the tensile strength of concrete. Because arch dams are constructed as cantilever monoliths, the joints between the monoliths cannot develop the tensile stress predicted in a linear analysis. In reality, the contraction joints are expected to open and close during an earthquake, releasing arch stresses and redistributing the internal forces. ADAP-88 is a finite element analysis program for computing the earthquake response of arch dams including the nonlinear effect of contraction joint opening. The nonlinear joint elements are combined with shell, solid and fluid finite elements to model a complete arch dam system. Special consideration is given to resolving the stress distribution near the joints by using a refined mesh of solid elements. A numerical procedure for solving the equations of motion assumes that the nonlinearity in the model is restricted to the joints. The cantilever monoliths between contraction joints are modeled as linear substructures, resulting in a significant reduction of computation in the iterative solution of the nonlinear equations of motion. ADAP-88 includes a finite element mesh generator for typical arch dam geometries. The computer program RESVOR is used to compute the added mass for the water impounded in the reservoir, assuming the fluid is incompressible.