Cognitive bias, i.e. overestimates of subjective probability and cost of catastrophic events, and irrational belief were explored as predictors of avoidance. Three groups-anxiety disordered clients, a mixed group of clinic outpatients, and normals--were administered several self-report inventories. Multiple regression analyses were used to investigate a modified version of the Agoraphobic Cognitions Questionnaire, the Belief Scale, and the Body Sensations Questionnaire as predictors of avoidance, as measured by the Mobility Inventory. It was hypothesized that frequency x probability x cost of catastrophic cognitions (and the occurrence of the events they represent) would be a better predictor of avoidance than frequency alone. It was also hypothesized that irrational thinking would be a significant predictor of avoidance. The results generally supported the hypotheses, with subjective probability emerging as a particularly potent predictor of avoidance. Theoretical and clinical implications are discussed.