Extra High Voltage (EHV) transmission corridor siting studies are complex and costly procedures, which are often prolonged by technical, public, institutional, and state regulatory factors. The primary goal of this research is to contribute to a more predictable and expedient siting study. The following objectives are accomplished: - Exploration and description of technical and methodological aspects of siting in terms of the general approach to the siting study, impact assessment techniques, data collection and mapping considerations. - Exploration and description of the following public and institutional considerations in the siting study: public participation, active opposition, media coverage, attitudes of affected agencies, and communication among involved organizations. Determination of the effects of these considerations on the siting process. - Review and evaluation of the state siting regulations in terms of: clarity of requirements, technical siting requirements, coordination of actions in the study, coordination with other relevant regulations, and public and agency participation in the study. Identification of the effects of the state regulations on the siting study process. - Development of guidelines for improved EHV transmission corridor siting studies. The principal methodology of the research is the single case study of Wyoming-Cloverdale 765 kV siting project, which represents a model of a contemporary, interstate, EHV siting study. The results of the case study are complemented by the review of state siting regulations and the literature. The major outcome of the research are the guidelines for improved corridor siting studies. The guidelines are developed for corridor siting study consultants, electric utility companies, and state regulatory commissions. Findings of the research indicate that technical, public, institutional, and state regulatory factors interactively affect the process of the corridor siting study. Furthermore, the siting study has dominant political overtones, and as such cannot be treated as a merely technical project. Public opposition to new EHV transmission lines can significantly increase the effects of technical, public, institutional, and regulatory deficiencies, reducing the probability of line approval. The testing of the guidelines in siting study practice, and a multiple case study research dealing with the same considerations and their interactions, are suggested for future research. / Ph. D.