Emergency personnel consistently work under high-stress situations, and thus, the question about whether this stress affects performance is critical to the safety of both themselves and the public. However, considerable controversy exists about the influence of stress on performance. This study investigates the association between both biological and psychological manifestations of stress and performance. The study was conducted with 84 police recruits using a high-fidelity simulation of a policing event in order to try to determine performance in a life-like workplace environment. Measures included both biological (heart rate and salivary cortisol levels) and psychological (subjective anxiety) indicators of stress. Performance was videotaped and was later evaluated by three expert raters. The results of this study are promising in that neither physiological nor psychological responses impaired performance in a simulated acutely stressful policing situation. On the other hand, those individuals with greater cortisol release showed higher levels of performance, supporting the notion that cortisol can enhance ability in high-stress situations. Recruits were also asked to subjectively evaluate their performance. A small group of individuals ranked themselves as poor performers while evaluators ranked them highly. These individuals experienced significantly higher increase in subjective distress and significantly higher cortisol levels at baseline and peak. Copyright © 2008 John Wiley & Sons, Ltd.