SummaryThe sports physician faces major practical problems in stimulating the activity of sedentary patients, and also ensuring their subsequent adherence to a prescribed exercise regimen. Both the individual and society bear some responsibility for poor exercise compliance. Patients are most likely to persist with programmes which are well-adapted to their physical, physiological, psychological and socioeconomic characteristics. The quality of leadership is also an important variable. Open-ended and structured questionnaires suggest that motivations to exercise include the improvement of health, the development of fitness, the control of bodyweight as well as an improvement in personal appearance, socialising, and simply a wish to ‘feel better’. The main perceived reason why people ‘drop out’ of formal exercise classes is through lack of time, although often the individuals making this complaint appear to have substantial free time. Personality characteristics of the adherent depend on the type of programme that is offered and the degree of social support that is provided; extraversion, a high self-esteem and self-motivation are common findings. Modelling of exercise behaviour has drawn upon the concepts of Skinner, Becker and most recently Fishbein. Beliefs and their evaluation seem more influential than subjective norms, although exercise behaviour is also heavily influenced by past experience of physical activity. Programmes should be designed to maximise external reinforcement of the exercise habit until the early discomforts of training are overcome, and the patient discovers the internal rewards of a more active lifestyle.