This dissertation addressed the predictability of performance under pressure through personality traits. Taking an interactionist perspective, the principle of trait activation was applied to the performance prediction. Because trait activation theorists suggest that only trait-relevant situational demands activate respective traits in (pres- sure) situations, situational demands of private, mixed, and public high-pressure situations were hypothesized to distinctly activate self-focus and self-presentation personality traits: Private and mixed (i.e., laboratory-based) high-pressure conditions would only activate self-focus traits (i.e., private self-consciousness), but not self-presentation traits (i.e., public self-consciousness, narcissism); and public high-pressure conditions would only activate self-presentation traits, but not self-focus traits. Low-pressure conditions would not activate any of the investigated personality traits. To empirically test these trait activation-based hypotheses, three consecutive studies were conducted that involved public (Study 1), private (Study 2), and private, mixed, and public (Study 3) high-pressure conditions. After participants had completed personality questionnaires, state-anxiety and performance on a throwing accuracy task were measured in low- pressure and high-pressure situations. State anxiety scores indicated successful pressure manipulations throughout the studies. Findings further supported the applicability of the interactionist principle of trait activation to the context of performance under pressure, because laboratory-based high-pressure situations only activated self-focus traits, public high-pressure situations only activated self-presentation traits, and none of the low-pressure conditions activated any of the personality traits. Hence, findings of this dissertation highlight that the simultaneous consideration of person and situation variables results in an improved (i.e., high-pressure situation-specific) prediction of performance under pressure through personality traits. Additionally, because public high-pressure situations distinctly differed from laboratory-based conditions in their trait activation ability, research on the personality/performance relationship should best take place in ecologically valid, namely public, scenarios.