The MMPI profiles of 96 male and 218 female patients attending a back pain clinic in a private university-affiliated, orthopedic hospital were analyzed by a hierarchical clustering procedure. The clustering procedure produced four male and four female profile subgroups. The subgroups were compared with one another on the basis of patients' responses to the Cornell Medical Index and revised McGill Pain Assessment Questionnaire. Within the male and female patient cohorts it was found that profile subgroups featuring elevated clinical scales showed greater disruptions of daily activities than did subgroups with relatively unelevated profiles. However, profile subgroups with elevations primarily on the neurotic triad scales reported greater affective disturbance and disruption of daily activities than did subgroups with elevations on both the neurotic triad and relatively psychotic scales. In addition, profile subgroups with subclinical elevations on the neurotic triad scales appeared to have adjusted to their pain experience more poorly than did subgroups that featured scores on nearly all clinical scales that were within one standard deviation of the mean. Suggestions are provided for the use of the MMPI in assessing chronic pain patients and future research regarding cluster analyses of patients' MMPI profiles.