The potential of physical exertion to enhance anxiety reduction was investigated by combining acute exercise with an imaginal exposure treatment for public speaking anxiety. Self-report, behavioural, and psychophysiological outcome measures all indicated that groups that received imaginal exposure improved more than those that received control procedures. The addition of acute exercise increased the treatment effect on two self-report measures (one for females only), although there was an indication of interference with change on one behavioural index. Multiple measures of process effects indicated that greater responding and greater habituation during treatment were associated with better outcome. Additional process measures indicated that enhanced imagery, altered attribution for arousal, and reduced energy were all associated with the addition of acute exercise to the exposure intervention. These findings support the value of imaginal exposure for reduction of speech anxiety, suggest that acute exercise may be of circumscribed value as an adjunct to such exposure, and offer possible directions for the study of the mechanisms responsible for exposure-based anxiety reduction.