Organisations providing secondary care in the NHS in England have historically not also provided primary health care, but this is changing. Data on where this kind of 'vertical integration' is happening are lacking, making it difficult to evaluate its impact. To compile a comprehensive list of instances of secondary care trusts running general practices in England, to enable evaluation of the impact of such arrangements. This service mapping study comprises review, collation, synthesis, and analysis of published information describing secondary and primary care provision in the NHS in England in March 2021. Desk-based collection, including hand-searching, of secondary care organisations' statutory annual reports. Triangulation via comparison with national data on general practices, the general practice workforce and practice contracts. It was possible to construct a database of all instances of trusts running general practices in England as of 31 March 2021. We have identified 26 trusts running a total of 85 general practices, operating across a total of 116 practice sites. These practices have on average fewer patients and fewer GP full-time equivalents than other general practices, and before becoming vertically integrated were performing less well in the Quality and Outcomes Framework. We recommend that national statistics recording the details of general practices contracting with the NHS should include whether each practice is owned by another organisation and whether that is an NHS trust, another public body, or a private organisation. Such data are required to enable evaluation of the impacts of this kind of vertical integration.