This thesis examined determinants and processes that are proposed to explain the mechanisms underpinning choking under pressure. The thesis is written as a series of three research papers, which are preceded by a general introduction in Chapter 1. An overview of the anxiety-performance literature is provided, within which specific areas that warrant further investigation arc highlighted. Two approaches to the study of choking under pressure are adopted within this thesis. The first attempts to understand the mechanisms underpinning the choking process, in which previous research has identified the Conscious Processing Hypothesis as one likely mechanism. The study in Chapter 2 reports an experiment that was designed to test the conscious processing hypothesis as an explanation for choking. Results revealed unexpected findings with regard to performance and the individual difference variables effort and confidence. These unexpected findings stimulated a reassessment of previous literature from an individual difference perspective. An imbalance between the two approaches was identified, resulting in the three subsequent studies of the thesis adopting an individual difference perspective. Chapter 3 consists of two studies that introduce choking as a personality disposition. A dispositional choking scale is developed in the first study, in conjunction with initial investigation into the influence of narcissism and trait self-consciousness. Study two reveals that dispositional choking predicts retrospectively reported state choking, and that narcissism moderates the relationship between trait selfconsciousness and choking. The final study in Chapter 4 further examines the precise nature of the interaction between narcissism and trait self-consciousness upon dispositional choking due to former contradictions, revealing support for previous theoretical perspectives (Baumeister, 1984; Wallace & Baumeister, 2002). Evidence also supports the argument that confidence does not fully explain the effects of narcissism. Theoretical and applied implications derived from this research are discussed, and recommendations for future research directions are presented to conclude.