Due to the critical nature of the application, diesel generator standby systems for nuclear power stations are required by law to be able to survive seismic disturbances and remain functional. Due to the large physical size and weight of this equipment, special considerations would have to be given, to arrive at a balance between reliability and cost. This paper describes the method used, the required engineering judgment and quality level of the results.Prior to the application of diesel generators as emergency standby power source for nuclear power plants, the effects of seismic disturbance were not seriously considered, although the diesel generators have proven over the years to be very reliable as well as durable in conventional applications. The application of diesel generators for nuclear standby power was relatively new and there was insufficient data available to develop any correlation between calculated and actual system response, or any form of design guide, for that matter.Due to the critical nature of the application, it is essential to insure that the diesel generator and its auxiliaries will survive seismic disturbances and remain functional whenever emergency power is called for. This created the need for seismic qualification which requires accurate analysis or test to attain the required level of reliability.