The Life Style Index (LSI), the Defense Style Questionnaire (DSQ), the Defense Mechanisms Inventory (DMI), and the FIRO Coping Operations Preferences Enquiry (FIRO) were administered to 187 undergraduates in order to determine convergent and discriminant validity of self-report measures of defense mechanisms. A correlational analysis of the four scales resulted in low correlations among subscales measuring similar defense mechanisms. A factor analysis produced factors based on particular scales rather than identical or similar constructs. Results suggest that self-report measures may not be an effective method for assessing various ego defense strategies.