Pretreatment measures of personality and symptom levels in agoraphobic subjects (N = 18) were correlated with their behavior on an interactive computer simulation that provided vicarious exposure to a phobia of elevators. Behavior during treatment sessions was assessed via human-computer interactions (HCIs). Automated programs analyzed these interactions to provide detailed behavioral descriptions. All subjects engaged in vicarious exposure, but the extent of this varied eightfold. Vicarious exposure increased across treatment sessions, with a qualitative shift to a high-exposure routine of staying in the simulated elevator and repeatedly traveling the maximum number of floors. The amount of activity spent on traveling in the elevator increased from 43% to 62% across three treatment sessions. Correlations were observed between vicarious exposure behaviors and a number of subject characteristics including neuroticism and conscientiousness. We conclude that HCIs provide a detailed record of behavior during computer-administered treatment. Subjects demonstrate learning of exposure strategies across treatment sessions. Interindividual differences in behavior correlate with a number of pretreatment subject personality characteristics.