A large and diverse number of treatments have been shown to be effective in reducing pain and other symptoms for a minority but statistically significant number of patients in different chronic pain syndromes. The means by which such different treatments achieve similar outcomes is not well understood. In this paper, the importance of considering patient heterogeneity for those who may be diagnosed with the same medical syndrome is discussed. The author suggests that the lack of satisfactory treatment outcomes for the treatments of chronic pain syndromes may be accounted for by the patient homogeneity myth-the assumption that all patients with the same medical diagnosis are similar on all important variables. The importance of subdividing (splitting) patients into meaningful groups is described. Studies presenting data on the identification of patient subgroups based on psychosocial and behavioral characteristics and the reliability and validity of this approach are presented. Some initial attempts to demonstrate the potential for matching treatments to patient subgroups are described.