MMPI (Form R) profiles of psychiatric inpatients (N = 45) meeting DSM-III criteria for borderline personality disorder were compared with chronic schizophrenic inpatients (N = 48) and with inpatients with acute psychotic illness (N = 20). Profile shape was similar among the three groups, although the borderline sample showed significantly higher elevations on four of the 10 clinical scales--Depression, Hysteria, Psychopathic Deviate, and Psychasthenia--when compared to the chronic schizophrenic cohorts. The borderline sample showed only one significant deviation on the clinical scales when compared to the acute psychotic sample as evidenced by a higher elevation on the Psychopathic Deviate scale. Clinically, the borderline MMPI responses suggest features of irritability, hostility, and resentfulness. On the validity scales, the borderline sample showed a significantly lower score on the L scale when compared to both comparison groups, although all of the groups' L scale scores were within conventional limits. While significant differences between groups did not emerge on the F scale, the borderline sample attained a clinically elevated score suggestive of weakened ego defenses and unconventional thinking. Analysis was also performed of a composite measure of psychoticism probability (the Goldberg Index) between groups. While the borderline and acute psychotic samples showed Goldberg indices suggestive of increasing likelihood for psychotic illness, the chronic schizophrenic group yielded a Goldberg Index significantly greater than both of the other groups, thus confirming the validity of the hypothesis. Finally, the MMPI borderline profiles were also compared to previously published norms of borderline outpatients and veteran borderline inpatients.(ABSTRACT TRUNCATED AT 250 WORDS)