The past 30 years have seen a fundamental shift in how psychopathology is understood, from a reliance on symptom-based psychiatric definitions to a greater emphasis on the phenomenology and basic mental operations underlying various forms of emotional disturbance. Much of the change in theory and therapy was set in motion by the original cognitive formulation of depression (Beck, 1967), an approach that over time has been extended to virtually the entire range of clinical problems. Specific domains within this general movement toward a greater phenomenological understanding of psychopathology have attracted considerable research interest and have developed into discrete domains of inquiry. Such is the case with the study of perfectionism, which is amply documented in the current volume.The aim of this chapter is to examine the advances made in the study of perfectionism against the background of the cognitive model and to consider whether some of the ideas emphasized in the model can shed additional light on the issues discussed in this book. In contrast to much of the material in this book, the cognitive model developed almost wholly out of clinical observation and owes relatively less t o the trait psychology and personality theory traditions. Furthermore, although global constructs like perfectionism, hopelessness, low self-esteem, and so on, are important components of the cognitive view of psychopathology, they typically are understood in reference to the basic mental operations they entail and the manner in which those operations are carried out.With respect to the emphasis on basic mental operations, a recurring observation in cognitive formulations of various emotional difficulties is that people undergoing such problems-and, often, those at risk-are likely to reason, problem solve, and interpret certain experiences in a rigid and arbitrary way. This mode of thinking manifests its4f through several avenues, and perfectionism is just one of them, albeit an important one. Furthermore, as an outgrowth of the emphasis on basic processes, the cognitive model has evolved in continual contact with developments in applied and basic psychology (see,