BACKGROUND:The use of electronic health records (EHR) is widely recommended as a means to improve the quality, safety and efficiency of US healthcare. Relatively little is known, however, about how implementation and use of this technology affects the work of clinicians and support staff who provide primary health care in small, independent practices. OBJECTIVE: To study the impact of EHR use on clinician and staff work burden in small, communitybased primary care practices. DESIGN: We conducted in-depth field research in seven community-based primary care practices. A team of field researchers spent 9-14 days over a 4-8 week period observing work in each practice, following patients through the practices, conducting interviews with key informants, and collecting documents and photographs. Field research data were coded and analyzed by a multidisciplinary research team, using a grounded theory approach. PARTICIPANTS: All practice members and selected patients in seven community-based primary care practices in the Northeastern US. KEY RESULTS: The impact of EHR use on work burden differed for clinicians compared to support staff. EHR use reduced both clerical and clinical staff work burden by improving how they check in and room patients, how they chart their work, and how they communicate with both patients and providers. In contrast, EHR use reduced some clinician work (i.e., prescribing, some lab-related tasks, and communication within the office), while increasing other work (i.e., charting, chronic disease and preventive care tasks, and some lab-related tasks). Thoughtful implementation and strategic workflow redesign can mitigate the disproportionate EHRrelated work burden for clinicians, as well as facilitate population-based care. CONCLUSIONS: The complex needs of the primary care clinician should be understood and considered as the next iteration of EHR systems are developed and implemented.KEY WORDS: electronic health records; primary care; work burden; qualitative research.