Abstract: A sliding roof system is proposed as a means to reduce dynamic response of buildings to earthquake excitations. In the system, frictional materials are inserted between the roof slab and the beams that support it. The roof slab and the beams are connected by springs. The optimum stiffness of the system is determined in such a way that the seismic response of the building is the minimum. A comparative study on the response of an eight-story frame structure with/without the proposed system to ground motions is carried out to assess the effectiveness of the system. It is found that the energy dissipation capacity of the system has nonlinear property. The effectiveness of the system is related to the frequency content and the acceleration value of the ground motion. The system reduces the maximum lateral displacement response and the maximum inter-story drift response of the analyzed building by as much as 45 percent on average except the roof.