In water resources development projects, dams are very vital structures whose safety against seismic forces has to be fully ensured by the designers. Along with critical stresses due to static loads, the dynamic stresses due to earthquake excitation constitute quite a significant part in the overall stress pattern in a dam. Stability analysis of gravity dams considering earthquake forces as equivalent static forces has become a standard practice amongst the designers. The pseudostatic approximation for the seismic forces are based on arbitrary seismic coefficients, which in turn are assessed on an estimate of the seismicity of the site. The characteristics of the structure to be analysed are however not reflected in these coefficients. The inadequacy of such arbitrary coefficients has been revealed by the experience of actual behaviour of dams during past earthquakes. The advent of spectral response method and the feasibility of complex computations with the help of high speed digital computers have made possible a rational structural analysis for dynamic loads. There is at present a keen awareness to adopt rational aseismic design procedures for analysis of such an important structure like a dam impounding huge quantum of water behind it. Such a rational analysis for dynamic loads has now necessarily become an integral part of the structural design of dams.