Obsessive compulsive disorder (OCD) remains one of the most challenging disorders of the brain. Contemporary conceptualization and therapeutic strategies are undergoing a revolution as a result of new insights derived from modern technological advances. This book was conceived in order to present this revolution to the reader. It covers current theories regarding the etiology of OCD, what is known about the genetics of this disorder, evidence from neuroimaging and a discussion of potential endophenotypes. There is an evaluation of current treatment approaches for the disorder, encompassing psychological, psychopharmacological and physical interventions, as well as a discussion of treatment resistance. The book considers methodological issues, plus reviews of OCD in pediatric populations. A summary chapter highlights some potential research avenues, in a discussion of the future directions in OCD.