BACKGROUND: Bond et al. developed the Defense Style Questionnaire (DSQ), a self-questionnaire that aims at empirically measuring conscious derivatives of defense mechanisms. The original analysis yielded 4 factors called Defense Styles (DS). DSQ discriminates between mature and immature defense styles. OBJECTIVES: Determine if the French version of DSQ has (a) face validity, (b) a similar structure to the original version, (c) internal consistency, (d) grouping of defense mechanisms into clinically pertinent defense styles, (e) evidence of nonpatients using more mature defense styles, (f) correlation with Defensive Functioning Scale (DFS) (DSM-IV) [2]. METHODS: Reliability and validity study on 82 control subjects and 140 patients, 59 among them evaluated for defensive level. RESULTS: Factor analysis of controls sample yielded 4 factors ranging from immature to mature defense styles. DSQ scores on factor I (maladaptive style) are significantly higher in outpatients than in controls. Maladaptive style score correlates with clinical evaluation of defensive level of functioning (DFS). CONCLUSION: Psychometric features of the French version are similar to the original scale, although minor differences in individual defense mechanisms are present. Factor I (maladaptive defense style) remains more stable than other factors, accounts for most of variance contribution, has high internal consistency and applies to behaviors, i.e. conscious derivatives of defense mechanisms that can be easily identified. The French version of DSQ is (a) an easy and economical way to rate immature defense style in populations of 'neurotic' and borderline patients and (b) further provides a hierarchical grouping of defense mechanisms in defense styles.