The behavioural therapies predominantly use exposure to feared stimuli in the treatment of anxiety disorders. However, clients frequently experience a return of fear after treatment and this may increase the likelihood of relapse occurring. Return of fear via a renewal effect is the most frequently studied source of return of fear. Renewal of fear occurs when the previously feared object is encountered in a context that is different to the treatment context. The present chapter reviews clinical-analogue studies that have investigated the renewal of fear. Prior research has confirmed the validity of renewal as a mechanism for the renewal of fear in high fearful and phobic individuals. Moreover, prior research has shown that factors such as phobic cognitions and pre-treatment fear can predict the likelihood of renewal of fear occurring. The review also highlights the methodologies used to detect renewal of fear and subsequently reduce renewal. Applications of the research to reduce the return of fear via renewal following exposure therapy are discussed.