Despite the existence of effective interventions for anxiety disorders, relapse - or the return of fear - presents a significant problem for patients and clinicians in the longer term. The present paper draws on the experimental and clinical behavioural literature, reviewing the mechanisms by which the return of fear can occur. The aim of the paper was to generate a list of treatment recommendations for clinicians aimed at reducing relapse in successfully treated anxiety disorders. Clinical and experimental literature on the mechanisms of renewal, reinstatement, spontaneous recovery and reacquisition are reviewed. These are linked with the clinical and experimental literature on the return of fear in successfully treated anxiety. A list of recommendations to assist in reducing the probability of relapse in successfully treated anxiety is presented. This list includes methods for use in behavioural (exposure) treatment of anxiety disorders that aim to enhance clinical outcomes. Despite the significant problem of relapse in successfully treated anxiety, there are methods available to reduce the probability of relapse through return of fear. Clinicians engaging in treatment of anxiety disorders should be mindful of these methods to ensure optimal patient outcome.