The transtheoretical model (TTM) is a behavioural theory that describes behaviour change as occurring in five stages, ranging from precontemplation to maintenance. The purpose of the present paper is to review and synthesise the literature published since 1999 on applications of the TTM to dietary behaviour so that the evidence for the use of assessment tools and interventions based on this model might be evaluated. Six databases were identified and searched using combinations of key words. Sixty-five original, peer-reviewed studies were identified and summarised in one of three tables using the following categories: population (n 21), intervention (n 25) and validation (n 19). Internal validity ratings were given to each intervention, and the body of intervention studies as a whole was rated. The evidence for using stage-based interventions is rated as suggestive in the areas of fruit and vegetable consumption and dietary fat reduction. Valid and reliable staging algorithms are available for fruit and vegetable consumption and dietary fat intake, and are being developed for other dietary behaviours. Few assessment tools have been developed for other TTM constructs. Given the popularity of TTM-based assessments and interventions, more research is warranted to identify valid and reliable assessment tools and effective interventions. While the evidence supports the validity of the TTM to describe populations and to form interventions, evidence of the effectiveness of TTM-based interventions is not conclusive. Transtheoretical model: Dietary behaviour: Nutrition behaviour: Weight management Introduced in 1981 1 , the transtheoretical model (TTM) has become one of the most popular and enduring theories in the field of health promotion and health education. The central concept within the theory is that behaviour change is most likely to happen when individuals engage in the right activities, or processes of change, at the right time, or stage. According to the theory, individuals are most likely to experience success in changing behaviour when they engage in strategies that are appropriate to their stage of readiness to make the change. It has been applied to diverse health behaviours, including the cessation of addictions, participation in cancer screening, and the adoption of positive lifestyle behaviours 2. Overview of the transtheoretical model Many published papers provide a detailed description of the TTM, therefore only a brief overview of the model is offered here. The TTM is comprised of the following constructs: stages of change, processes of change, decisional balance, self-efficacy, and temptation. Stage of change refers to the degree of readiness an individual exhibits toward adopting healthful dietary behaviours. A generalised version of the five stages has been identified and used to classify behaviour 3. The stages are: (1) precontemplation, in which an individual may or may not be aware that a behaviour change is warranted and has no intention of changing within the next 6 months; (2) contemplation, ...