This work has the aim of making facet theory, and the approach to research which derives from it, more accessible to behavioral and social scientists than has been possible in the past. In a first section the book gives the background to the theory and associated methods of analysis, illustrating the major components of the ap proach in use. A second section then provides detailed examples of the applications of the facet approach in developmental, clinical, and environmental psychology, as well as in studies of attitudes and mental performance. The third section provides some further technical details on recent developments in the facet approach as well as a computer program listing. The facet approach to social and behavioral research can be traced at least to the late 1940s (as discussed by Gratch, 1973) and the logical principles on which it is based have clear roots in Descartes'' algebra and Fisher''s experimental designs.