Abstract:Background: Multisource feedback (MSF) is increasingly being used as one of the components in revalidation and recertification processes to guide physicians' continuing professional development. Data provided by coworkers (e.g., nurses, pharmacists, technicians) are recognized as integral for assessing a physician's communication, teamwork and interprofessional abilities. The purpose of this study was to examine both the reliability of co-worker scores and the association between co-worker familiarity and physician ratings as both affect perceptions of the quality of feedback and the likelihood that recipients will take their feedback seriously.