There is currently no classification system for chronic pain patients that has achieved consensus. The lack of a classification that is used consistently across settings has impaired advance of knowledge and treatment of chronic pain patients. Recently, an empirically derived multivariate classification system, the Multiaxial Assessment of Pain (MAP) patients, has been developed. In this paper, the generalizability of the MAP system was evaluated by contrasting the MAP classification of 3 common but diverse chronic pain syndromes, namely, low back pain, headache, and temporomandibular disorders. The results indicate that although the proportion of patients classified into the 3 subgroups of the MAP taxonomy differ, the profiles based on the pattern of interrelationship among the assessment scales were remarkably similar. These data suggest that the psychosocial and behavioral responses associated with chronic pain are common to diverse samples of pain patients despite differences in demographic characteristics and medical diagnosis. The implications of these results for research and clinical practice are discussed. The potential utility of a polydiagnostic approach using more traditional medically based classifications such as proposed by the IASP (Merskey, H., Pain, Suppl. 3 (1986) S1-S225) complemented by classification based on the MAP psychosocial-behaviorally based taxonomy are examined.