While clinical approaches to anxiety disorders are typically categorical, a more dimensional perspective to understanding the psychobiology of anxiety and its dysfunction may prove of increasing importance. A dimensional approach is supported by evidence of the value of a transdiagnostic approach to the evaluation of anxiety and related symptoms, to the assessment of neurobiological and cognitive–affective profiles, and to treatments for anxiety conditions. This chapter provides a conceptual basis for approaching key psychobiological dimensions thought to underpin the anxiety disorders. The chapter outlines, in turn, spectrum approaches to the assessment of anxiety, dimensional approaches to research on mechanisms underlying anxiety disorders, and transdiagnostic approaches to treatment. While categorical approaches have clinical utility and are likely to remain key, dimensional approaches may hold particular promise for informing translational research in the future.