The changing shape of the traditional buyer–supplier relationship between independent medical practices, or office-based physicians, and medical industry suppliers has prompted the proliferation of Internet-based purchasing applications. Healthcare informatics researchers believe that such systems hold great promise for improving the efficiency of medical organizations. We surveyed 216 medical practice adopters of electronic purchasing, to assess the post-adoption benefits following system assimilation. Results showed that Internet-based purchasing applications had a positive impact on both claims management and operational performance outcomes. Moreover, we found that compatibility, facilitating conditions, the IT infrastructure, and preference item purchasing were necessary antecedents to effective Internet-based purchasing application assimilation