Procedurally Virtual reality exposure therapy (VRET) is quite similar to models of extinction of conditioned fears. Recent advances in animal research have identified pharmacological agents that appear to both accelerate and consolidate extinction learning. One of these cognitive enhancers is Yohimbine. An interesting finding in animal literature is that the administration of Yohimbine during extinction trials accelerates fear reduction and may convert ineffective exposures in to successful ones. It is thought that the mechanism of enhanced emotional memory is through elevated norepinephrine in the prefrontal cortex. Therefore, we propose to extend these studies by combining VRET with Yohimbine. In this pilot study with a between groups design 20 participants with a fear of flying will be treated with VRET plus Yohimbine or VRET plus placebo. This between groups design was chosen to further characterize the differential within and between trial extinction. Outcome will be measured by self-report, behavioral, and psychophysiological assessments at pre- and post-treatment. In addition, we will examine extinction parameters during exposures.