THE MMPI AND THE EPPS ARE MULTI-SCALE PERSONALITY INVENTORIES FREQUENTLY EMPLOYED IN THE DIAGNOSTIC AND TREATMENT PROCESS. THE MMPI WAS DERIVED EMPIRICALLY TO DIFFERENTIATE SELECTED CLINICAL GROUPS AND THE EPPS WAS DEVELOPED WITH THEORETICALLY MORE ADJUSTED ADULTS TO MEASURE NEEDS SELECTIVELY OBTAINED FROM MURRAY'S NEED STRUCTURE THEORY OF PERSONALITY. YET THE MMPI IS MORE FREQUENTLY EMPLOYED IN THE CORRECTIONAL PROCESS THAN THE EPPS. A REPRESENTATIVE SAMPLE OF 400 INCARCERATED OFFENDERS WAS ADMINISTERED THE MMPI AND THE EPPS CONCURRENTLY. CORRELATIONAL RESULTS WERE ANALYZED WITH A PRINCIPAL FACTORING METHOD AND ROTATED OBLIQUELY TO MEET SIMPLE STRUCTURE CRITERIA. OF THE NINE BIPOLAR FACTORS EXTRACTED, THREE WERE PRINCIPALLY MMPI, AND FIVE WERE MAINLY EPPS IN NATURE. BECAUSE MOST OF THE FACTORS HAD BEEN OBTAINED FROM OTHER POPULATIONS, THE IMPLICATION IS THAT INCARCERATED OFFENDERS DIFFER MORE IN DEGREE THAN TYPE FROM OTHER SAMPLES. MMPI AND EPPS BOTH CONTRIBUTE UNIQUE VARIANCE TO PERSONALITY ASSESSMENT, AND THE EPPS, IF VALIDATED FURTHER, COULD BE EMPLOYED MORE PRODUCTIVELY WITH INCARCERATED OFFENDERS. PREDICTIVE VALIDITY RESEARCH, PARTICULARLY WITH THE EPPS, APPEARS TO BE NEEDED WITH VARIOUS OFFENDERS. REFERENCES, FOOTNOTES, AND TABLES SUPPLEMENT THE TEXT. (AUTHOR ABSTRACT MODIFIED)