Is it possible to ban unwanted thoughts from consciousness? According to the literature on thought suppression, the answer is no. In the 1980s, Wegner and colleges demonstrated that the average person cannot prevent a trivial thought like that of a polar bear from entering consciousness approximately seven times in a five minute period. This experimental finding was followed by a substantial number of replications. This book provides an up-to-date overview of the thought suppression literature. First, similarities and differences between suppression, repression, and dissociation are discussed. Methodological issues are then considered. Finally, the clinical applications of the thought suppression literature are discussed. Although there are numerous conditions to which the phenomenon of suppression can be applied, obsession and traumatic recollection are the main applications. In addition to offering an overview of the literature, this book links the thought suppression paradigm to other research fields, such as directed forgetting and repressive coping. Furthermore, it discusses the phenomenon of thought suppression in the light of broader theories such as the cognitive theory of obsession, and the ego depletion hypothesis. Clinical implications and directions for future research are offered.