Acquisition of physician practices by private equity firms has accelerated, 1,2 with unknown implications for care delivery and patient outcomes. However, available data are limited to single specialties or come from industry reports or opinion articles. A dearth of evidence and the use of nondisclosure agreements at early stages of negotiation have constrained the ability to evaluate this phenomenon empirically. 3 In this study, we describe physician group practices acquired in 2013-2016 across specialties. Methods | We identified US physician group practice acquisitions by private equity firms using the Irving Levin Associates Health Care M&A data set, 4 which includes manually collected and verified transactional information on a broad set of health care mergers and acquisitions. We excluded practices bought by entities not classified as private equity firms at the time of acquisition. We verified practice names, locations, specialties, and group practice status via Google searches. We linked acquisitions to the SK&A data set, a commercial data set of verified physician-and practice-level characteristics (eg, specialty, credentials, practice ownership, size, and locations) for US office-based practices. Transactions Key limitations include that the data are based on publicly announced transactions and therefore underestimate total acquisitions, particularly of smaller practices, and that available data lag behind the rapid pace of private equity acquisitions.