In this study, patients with neurotic disorders, borderline patients, acute schizophrenics, and chronic schizophrenics were studied with regard to primitive defense mechanisms. Primitive defense mechanisms were assessed by means of the Lerner Defense Scale (LDS). In this study, the LDS was applied to the Holtzman Inkblot Technique. With the exception of primitive idealization, borderline patients used all primitive defense mechanisms significantly more frequently than patients with neurotic disorders, that is, splitting, projective identification, primitive denial, and primitive devaluation. Compared with both acute and chronic schizophrenics, borderline patients used primitive devaluation at a significantly higher degree of frequency. Both acute and chronic schizophrenics differed from patients with neurotic disorders by using splitting and projective identification significantly more frequently. However, there were differences concerning primitive devaluation and idealization. The defense structure of chronic schizophrenics was heterogenous. Except for primitive idealization, all primitive defense mechanisms correlated significantly with self-report measures of identity diffusion and impaired reality testing, which is consistent with theoretical assumptions. By a discriminant analysis, 90% of the borderline patients, 80% of the patients with neurotic disorders, 76% of the acute schizophrenics, and 92% of the chronic schizophrenics were classified correctly.