The primary aim of the present thesis was to investigate the role that individual and situational factors play in moderating the impact that pre-event expectancies have on judgements of a tennis player's performance. The current programme of research utilised a between subjects design with competitive tennis players (Studies 1 and 2) and undergraduate volunteers (Studies 3, 4 and 5) being assigned to one of four experimental conditions in each study. The results of Study 1 supported past research findings (Buscombe et al., 2006) confirming the role that body language plays in influencing the impressions formed of tennis players. However, the results did not demonstrate expectancy effects with early judgements of a performer failing to influence subsequent ratings of that individual's play. Study 2 found that the participants' level of trait confidence and trait anxiety did not moderate the impact of body language on judgements of performance. Study 3 demonstrated an interaction between body language and time pressure (F(l, 53)=12.00, p=.OOl) such that when under time pressure the participants rated the target's play more favourably having previously viewed the player displaying positive (M=42.76, SD=7.25) as opposed to negative (M=24.2S, SD=5.lS) body language. As such, it was concluded that time pressure may serve to moderate expectancy effects in sport. Study 3 also indicated that a perceiver's dispositional need for closure did not exert any influence over judgments of the performer. Study 4 demonstrated that increasing the participants' accountability for their judgements did not moderate expectancy effects. However, in line with the results of Study 3, the player's body language was seen to influence ratings of that individual's performance. Employ a reallife target performer, Study 5 demonstrated that prior knowledge of the target player's recent win/loss record influenced the participants' subsequent ratings of that individual's performance (F(l, llS)=lO.72,p=.OOl). Specifically, the participants' ratings of play were more favourable having been presented with a positive (M=41.7, SE=.S7), as opposed to a negative (M=37.74, SE=.S3) prior playing record for the performer. Overall, the thesis indicates that expectancy effects are evident in sport and that the length of time permitted to a perceiver to form a judgement of an athlete may moderate these effects. This thesis provides the first structured examination in the extant literature of the role that individual and situational factors play in moderating expectancy effects in sport. Furthermore, the thesis provides the first indication that expectancy effects may be witnessed in real-life contests between two sports performers.