This authoritative book reviews current cognitive-behavioral models of OCD & delineates an innovative theoretically & empirically grounded approach to assessment & treatment. Leading scientist-practitioner David A. Clark first elaborates & refines existing theories of obsessions & compulsions. He then spells out effective strategies for assessing client needs developing a clear case formulation implementing an array of cognitive & behavioral interventions & troubleshooting potential difficulties. Illustrated with extensive clinical material the volume is practical & user-friendly. Reproducible appendices feature over a dozen rating scales client handouts & homework tasks.