Cardiac rehabilitation (CR) programmes typically offer patients with heart disease a long-term programme of medical evaluation, exercise, education and counseling. National guidelines have recognized the positive impact that attendance at CR can have following heart attacks, angina and other heart problems. Patients who attend such a programme have been shown to have reduced health problems. Despite this, research suggests that the use of these services is poor and that the majority of patients eligible for these programmes do not continue to attend after their first class. A range of factors have been associated with non-adherence to CR, including psychological factors such as people's beliefs about their illness. For example, patients with high levels of perceived control over their illness after a heart attack appear to be more likely to attend CR classes than those with low levels of perceived control. Such findings suggest that changing patients' illness beliefs, specifically those associated with illness control and illness consequences, could help to increase adherence to CR programmes. Increased adherence to CR could improve health outcomes for patients with cardiac illnesses. The present study is therefore investigating the effectiveness of a one-session psychological intervention, based on a theory called the Self-Regulatory Model, in altering beliefs about illness among patients starting cardiac rehabilitation. Participants will be randomly assigned to a treatment or a non-treatment group. It is hoped that those who receive the treatment session will attend more CR classes.