The main source for the database is the "Annals" of the College, which are a record, at first in Latin and then increasingly in English, of its meetings and of selected correspondence, kept by the College's Registrar. This record is incomplete before 1580, when administrative reforms were introduced. Details relating to irregular practitioners are also limited for the period between 1608 and c. 1614, when a separate Book of Examinations was used (now lost). Information from the Annals was initially extracted directly from the Annals; subsequently, it became possible to amplify these data when microfilm became available of the translation/transcription of the Annals carried out for the College by J. Emberry and S. Heathcote (1953-5). Partial checks were also carried out against the original Latin and English text, which became available on microfiche in the course of the project.
The information from the Annals has been supplemented by prosopographical data taken from a card-based Biographical Index of medical practitioners in London and East Anglia, begun and continued in the Wellcome Unit for the History of Medicine, University of Oxford, under the direction of Dr Charles Webster, and now in the custody of Dr Margaret Pelling (Modern History Faculty, University of Oxford).