In this study, we investigated the factor structure of situational fears in agoraphobia by examining four models of the Avoidance Alone items in the Mobility Inventory for Agoraphobia. A main sample of 327 agoraphobic patients and an independent control sample of 64 agoraphobic patients were studied. A confirmatory factor analysis supported a four-factor model including a public places, an enclosed spaces, a public transportation, and an open spaces factor both for pre- and posttreatment data. The convergent and divergent validity of subscales derived from the four factors were supported by an expected pattern of correlations with interview-based measures. These subscales also proved to have satisfactory internal consistencies in the independent sample.