About 49% of health referrals involved health information exchanges (HIEs) via electronic summaries of care (eSCR) during 2016, according to health care professional attestations for the federal Meaningful Use electronic health record (EHR) incentive program. Primary care professionals used HIE to make 43% of referrals, compared to 57% among professionals not in a primary care specialty. Practice-level factors were more commonly associated with greater levels of HIE use than market-level factors. The practice factors linked to greater use of HIE for referrals were as follows: Higher share of older consumers Higher share of consumers . . .