The adoption of health behaviours is essential if coronary heart disease patients are to optimise their chance of survival and reduce the likelihood of recurrent coronary events. However, this behavioural change may not ensue following an acute myocardial infarction(AMI). This study on first AMI subjects sought firstly to examine the psychometric properties of five scaled instruments used for assessing health behaviours. Secondly, the study assessed the prevalence of health-enhancing behaviours at the time of the first AMI and 6 months after this event.Thirdly, the magnitude of health behavioural change was then examined. Fourthly, sociodemographic, clinical and psychosocial predictors of health-enhancing behaviours were explored.These health-enhancing behaviours included non-smoking behaviours, normal body mass index (BMI), adequate physical activity, medication adherence and low dietary fat intake. Finally, the study examined relationships between sociodemographic , psychosocial and modifiable lifestyle factors, based on Antonovsky's hypothesis on sense of coherence(SOC), stress and adaptive coping. The study highlights that some modifiable risk factors, for example, being overweight or obese and physical inactivity were more resistant to change following an AMI.This finding, and the relationship between stress and increased dietary fat suggest a need for individualised programs to support the specific needs of AMI patients to change their modifiable cardiac risk factors. / Doctor of Philosophy (PhD)(Health)