This thesis is concerned with the performance of electric power transformers and their attachments under earthquake loading. It begins with the description of the transformers, attached bushings, and some typical examples of substation failures in earthquake loading. This is followed by the development of finite element model of three different sizes of transformers. Finite element models consist of several thousand degrees of freedom and they are basic to this thesis. Some of the major findings from these models are utilized to derive a simplified model of a portion of a substation, The frictional pendulum system (a base isolation method) is considered for rehabilitation of existing substations or the mitigation of the seismic requirements for new substations. Results of parametric and experimental study are presented. A simplified model of a transformer with its appendages developed for use in engineering offices is developed and responses of fixed base and isolated transformers are compared. Based on the results of this study, the use of base isolation or anchorage for transformers is suggested. Finally, modifications of the IEEE specifications for qualifications tests for transformers and bushings are proposed.