This research has investigated exercise adherence from the perspective of Cognitive Evaluation Theory (CET: Deci & Ryan, 1985a). In particular, the motivational consequences of internally controlling and internally informational modes of behavioural regulation was explored with respect to the kinds of exercise goals that individuals adopt. It was proposed that goals will influence intrinsic motivation for exercise to the extent that they are controlling or informational in nature. The first part of the thesis describes conceptual and operational issues and the development and validation of measures of perceived locus of causality (the Locus of Causality for Exercise Scale: LCE) and participation motives (the Exercise Motivations Inventory: EMI). In addition, the psychometric -integrity of the Intrinsic Motivation Inventory (IMI: McAuley et al., 1989, 1991) was examined. Results suggested that the LCE and the EMI possessed reasonably good factorial and construct validity. However, questions were raised about the theoretical underpinnings and item content of the IMI. The second part of the research involved an intervention in which subjects were trained to set effective, personally-controllable goals for exercise. Results showed that goal-setting training was not superior to an attentioncontrol procedure, with both treatments leading to a significant increase in exercise levels. However, large individual differences were noted in the effects of both treatments. These were explained in terms of Causality Orientations Theory (Deci & Ryan, 1985a), which proposes that people differ in the extent to which they seek to be autonomous or controlled in the regulation of their behaviour. Follow-up analyses supported this interpretation. The results of the research programme suggest that the internally controlling/internally informational distinction is important in the exercise context, but that CET, and the more wide-ranging Self-Determination Theory of which it is a part, suffer from a degree of conceptual confusion and operational difficulties which need to be addressed if progress is to be made in understanding and explaining exercise behaviour.