This study was designed to investigate runners' perceptions of arousal and awareness of physiological responding before and after a 20-kilometer (12.4-mile) race. Participants (N = 98) completed pre- and postquestionnaires that included measures of awareness of physiological responding and self-defined states of activation and arousal. In order to identify those variables related to performance, the finishers were divided into three groups: fast, moderate, and slow. A discriminant analysis revealed that miles run in training each week, resting pulse rate, and weight were the best predictors of group membership. Of the several psychological variables, only prerace tension discriminated between the groups, with the faster runners reporting themselves as more fearful and "clutched-up" before the race. In terms of pre-post physiological and psychological effects, it was found that running 20 kilometers resulted in a significant, increased awareness of physiological responding, increased feelings of being tired and relaxed, and decreased feelings of tension and energy. These findings are discussed in terms of their implications for future research.