Background: Prior research has examined clinical effects of performance measurement systems. To the extent that non-clinical effects have been researched, the focus has been on negative unintended consequences. Yet, these same systems may also have ancillary benefits for patients and providers - that is, benefits that extend beyond improvements on clinical measures. The purpose of this study is to identify and describe potential ancillary benefits of performance measures as perceived by primary care staff and facility leaders in a large US healthcare system. Methods: In-person individual semistructured interviews were conducted with 59 primary care staff and facility leaders at four Veterans Health Administration facilities. Transcribed interviews were coded and organised into thematic categories. Results: Interviewed staff observed that local performance measurement implementation practices can result in increased patient knowledge and motivation. These effects on patients can lead to improved performance scores and additional ancillary benefits. Performance measurement implementation can also directly result in ancillary benefits for the patients and providers. Patients may experience greater satisfaction with care and psychosocial benefits associated with increased provider - patient communication. Ancillary benefits of performance measurement for providers include increased pride in individual or organisational performance and greater confidence that one's practice is grounded in evidence-based medicine. Conclusions: A comprehensive understanding of the effects of performance measurement systems needs to incorporate ancillary benefits as well as effects on clinical performance scores and negative unintended consequences. Although clinical performance has been the focus of most evaluations of performance measurement to date, both patient care and provider satisfaction may improve more rapidly if all three categories of effects are considered when designing and evaluating performance measurement systems.