This paper reviews the research literature on MMPI assessment of functional versus organic low back pain (LBP). Research is described in three categories: (a) the relationship between psychopathology as measured by the MMPI and low back pain, (b) MMPI speciality scales, and (c) surgical outcomes. Research, to date, has suffered from methodological problems which has limited generalizations to clinical population. It is suggested, however, that the MMPI can be effectively used with LBP patients, but should not be the only data used in such assessments. Cautions are noted regarding use of the speciality scales.