This longitudinal study identified processes of exercise behaviour change (POC) associated with movement between the stages of exercise behaviour change (SOC). Participants' (N = 312) physical activity, SOC and POC were recorded at baseline, one, three, six and 12 months post-test. Following baseline, participants received one of three physical activity interventions. The process of self-liberation was important at each stage movement. The process of stimulus control appeared important when progressing from contemplation to preparation. Progression from action into maintenance was associated with increased use of social liberation and helping relationships. The study indicated the transtheoretical model is applicable to a British population.