Among the repertoire of clinical skills necessary for the professional development of medical students is the ability to create a positive doctor-patient relationship through effective communication skills. The purpose of this study was to create an instrument that reliably measures the relationship between physician and patient. The Relationship Instrument provides evidence to document both medical student's task and socio-emotional behaviors as well as the socio-emotional behaviors of the patients whom they interview. Specifically measured were indicators of this relationship between third year medical students taking a clinical performance examination and standardized patients. Subjects (n=370) included all third year medical students at four medical schools in North Carolina. The Relationship Instrument is a 15-item checklist that was completed by a standardized patient in each of 20 cases. Exploratory factor analysis did identify a two factor model that used 13 of the original 15 items and indicated that scores derived from the Relationship Instrument correspond to the two dimensions used to construct it. Factor scores on the instrument were reliable. Thus, evidence suggests that measurements derived from the Relationship Instrument are consistent with interpretation of the two components of the doctor-patient relationship. A copy of the instrument is included. (JBJ)