The Health Information Technology for Economic and Clinical Health Act recently catalyzed the adoption of electronic health records (EHRs) in both hospital and ambulatory settings. Overall, EHRs have positively affected patient safety, but this effect has been inconsistent. This qualitative study explored whether differences in individual physicians' traits affected their EHR-use patterns in the ambulatory setting. Physicians were categorized as either "uncertainty reductionists," "uncertainty absorbers," or "uncertainty hybrids," based on how they viewed the role of patient information in the medical record and how they handled uncertainty. Physicians who viewed uncertainty primarily as reducible through information ("reductionists") tended to be high EHR users; whereas, those who acknowledged irreducible uncertainty in caring for patients ("absorbers") were mostly low EHR users. These findings have implications for future EHR implementation and training efforts. Dr. David Blumenthal discussed health information technology adoption in an AHRQ WebM&M interview.