With the lack of timely and relevant patient information at the point of care increasingly being linked to adverse medical outcomes, effective management and exchange of patient data has emerged as a strategic imperative for the healthcare industry. Healthcare informaticians have suggested that electronic health record systems (EHRS) can facilitate information sharing within and between healthcare stakeholders such as physician practices, hospitals, insurance companies, and laboratories. We examine the assimilation of EHRS in physician practices through a novel and understudied theoretical lens of physicians' identities. Physician practices and the physicians that lead them occupy a central position in the healthcare value chain and possess a number of unique characteristics that differentiate them from other institutional contexts, including a strong sense of affiliation with other physicians, potent professional identities, and a desire for autonomy. We investigate two salient physician identities, those of careprovider and physician community, grounded in the roles physicians play and the groups with which they affiliate. We argue that these identities and their evolution, triggered by EHRS, manifest as both identity reinforcement and deterioration, and are important drivers of EHRS assimilation. We use survey data from 206 physician practices, spread across the United States, to test our theoretical model. Results suggest that physician community identity reinforcement and physician community identity deterioration directly influence the assimilation of EHRS. We further find that the effects of careprovider identity reinforcement and careprovider identity deterioration on EHRS assimilation are moderated by governmental influence. Theoretical and pragmatic implications of the findings are discussed.