Scholars have often assumed that the Eusebian apparatus was defunct and ignored in the Middle Ages. I argue, however, that Greek manuscripts offer evidence for readers’ ongoing use of the Eusebian apparatus. While the transmission of the Eusebian apparatus was subject to error, users maintained the functionality of the Eusebian system. Readers adapted the apparatus in order to make it a better resource for their reading of the gospels. Transformations of the Eusebian system are part of its reception history, illuminating how readers used Eusebius’s project. They demonstrate both the continued vitality of the apparatus and medieval readers’ vibrant interest in comparative studies of the gospels.