ABSTRACT: BACKGROUND: Touted by some as reflecting a better medical model and cited by the influential IOM report in 2000 as one of the six domains of quality care, patient-centered medicine has yet to fully establish its scientific attributes or to become mainstream. One proposed reason is failure to behaviorally define what the term 'patient-centered' actually means. OBJECTIVES: (1) To identify patient-centered articles among all reported randomized controlled trials (RCT); (2) to identify those with specific behaviorally defined interventions; (3) to identify commonalities among the behavioral definitions; and (4) to evaluate the relationship of the well-defined RCTs to patient outcomes. DATA SOURCES: Medline from April 2010 to 1975. ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONS: RCTs having any specific, behaviorally defined patient-centered skill(s) in an intervention with some patient outcome involving real adult patients and providers in real clinical situations. APPRAISAL AND SYNTHESIS METHODS: Critical appraisal via narrative review. RESULTS: The prevalence of any mention of patient-centeredness among 327,219 RCTs was 0.50% (1,475 studies), from which we identified only 13 studies (0.90%) where there were behaviorally-defined patient-centered skills in an intervention. Although there were too few studies to make clinical recommendations, we identified common features of the behavioral definitions used: all went well beyond identifying individual skills. Rather, skills were grouped, prioritized, and sequenced by virtually all, often describing a stepwise patient-centered approach to, variously, gather data, address emotions, or inform and motivate. LIMITATIONS: The inherent subjectivity of our method for identifying behaviorally-defined studies could under- or over-represent truly replicable such studies considerably. Also, studies were few and very heterogeneous with interventions of widely differing intensity and foci. CONCLUSIONS AND IMPLICATIONS: RCTs identified as patient-centered were rare, and <1% of these were behaviorally defined and, therefore, possibly replicable. There were many common behavioral definitions in the studies reported, and these can guide us in identifying agreed-upon patient-centered interventions, the immediate next-step in advancing the field.