The CPL database gives access to 714 practitioners of medicine, male and female, whom the College of Physicians of London (CPL) sought to prevent from practising physic in London between 1550-1640. The database also provides some access to the physicians (all male) who were members of the College during this period. The two groups are loosely described as "Fellows" and "felons" : in fact, members of the College included Candidates, Licentiates and Extra-Licentiates as well as Fellows, and unlicensed practice was not in legal terms a felony. A significant proportion (all male) were both Fellows and "felons" ; that is, although at one time charged with being unlicensed, they later became members of the College. In terms of education and qualifications, the unlicensed or irregular practitioners varied from women with no formal education, to men who were as well qualified as any member of the College. Many irregulars were London barber-surgeons and apothecaries who saw it as their right to practise physic. Most if not all of these are likely to have been literate. Others were much-travelled, cosmopolitan scholars, or religious refugees. Some of the irregulars were born outside England; many more (like the College members themselves) qualified (or spent time) in non-English universities. The irregulars were arguably more cosmopolitan than the College itself. The diversity of the irregulars reflects both medicine's usefulness as a portable skill in universal demand, and the status of London as one of the largest, fastest-growing European capitals, a centre for services such as medicine and law, and a focus of attraction for immigrants from the English provinces and continental Europe.
The names of many of the irregulars reflect this mutability: they were Latinized or Englished, often the (difficult) last name of "stranger" practitioners was dropped and only the more familiar first name used, or the name was spelt in a variety of ways according to how it was heard. The database selects a single version of each name, but also records variants.
The complete database also gives access to the names of patients, witnesses and others, as well as the illnesses or conditions mentioned, and the treatments which the practitioner was alleged to have used.