Background: Reinforcement Sensitivity Theory (RST) is a theory which proposes that three basic neurophysiological systems explain and predict individual differences in personality, behaviour and experience of distress. Two of these systems are sensitive to aversive and appetitive stimuli respectively, and mediate avoidance and approach behaviour. The third is a conflict resolution module activated by conflict between and within the other two systems, and it mediates cautious approach and threat assessment. Aims: To present an overview of RST and to outline how RST theory and research can be of use to patients, clinicians and clinical researchers in the field of mental health. Method: Recent literature is reviewed to give an overview of the origins of the theory, followed by an account of how the three RST systems might explain different distress disorders, including anxiety and depression, phobic disorders and impulse control disorders. The RST distinction between anxiety and fear is described, and its relevance to the understanding of common distress disorders is outlined. Finally some of the clinical implications of the theory are considered alongside recent developments in cognitive behavioural therapy. Conclusion: It is concluded that RST is a theoretically and practically useful explanatory framework for patients, clinicians and researchers.