The open access model, defined here as free access to scholarly publishing, has emerged alongside the traditional, subscription-based model for publishing medical journals [1–3]. The open access model was developed largely in response to rapidly rising subscription prices [4, 5], which raised concerns about access to scientific research, especially that funded by public entities [2]. In 2003, Public Library of Science (PLoS) launched a nonprofit scientific and publishing venture producing open access journals with no charge for access and, other than appropriate citation, no restrictions on use [6]. Funders of biomedical research, including the National Institutes of Health (NIH), also pushed for open access to research they support. In 2007, the NIH public access policy was signed into law, requiring that all investigators funded by NIH have an electronic version of their final manuscripts publicly available within twelve months of publication [2]. Despite the emergence of open access, knowledge of the finances of medical journal publishers is limited [4]. Published reports have surveyed open access journals, described their business models, and reported their finances [1, 7] but have been limited by their scope or have been disproportionately weighted away from for-profit publishers [1]. This study therefore sought to increase understanding of the finances of the publishers of the most highly cited US general and internal medicine journals by examining the tax status, revenue, expenses, and operating margins in order to inform public debate and policy.