A methodology was developed and applied to identify the principal candidate sites at which major steam electric generating facilities to serve the Long Island area could be located. The selection criteria included not only economic and engineering considerations but social and environmental factors refleeting changing and often intangible public values. From 68 candidate sites, five were selected through a series of steps in which analysis and judgment were combined to overcome the problems of preliminary information and uncertainty. These successive steps eliminated unsuitable sites on the basis of a qualification review and a preference review. A refined analysis of the favorable sites revealed patterns of value-free dominance among them.