He knew venereal disease as he knew a range of other diseases, which is to say, very much as contemporary physicians knew them. Again there was nothing unique about his concentration on this subject; much the same can be said for his knowledge of the law, not to speak of statecraft and the arts of war. There is extant a scholarly paper expounding the mathematics of the odds propounded by Claudius and presented to Hamlet by Osric before the duel.

Shakespeare's knowledge of medicine has been documented in a book by a Scottish surgeon, R. R. Simpson, Shakespeare and Medicine (1959). Simpson in turn acknowledges the aid of an earlier study by John Bucknill, dated 1860. Simpson says, "Shakespeare's knowledge of medicine corresponded closely to that prevailing at his time among its professors," being still heavily influenced by Hippocrates and Galen. Yet just as the poet seemed to know nearly everything else that was known in his time, evidently from his own observation as well as from books, so he must have enlarged his knowledge of medicine by what he saw around him. We know that his son in law, who married Susanna in 1607, was a physician, reputedly one highly skilled and trusted; but he does not seem to have been important as a source of Shakespeare's information. John Hall arrived in Stratford about 1600; Shakespeare's medical references in the plays reached a peak in Romeo and Juliet (1594 1595). In specific references, for instance to drugs, there is little evidence of any influence of Hall, whose own writings on medicine were not recorded until 1617, a year after Shakespeare died. Hall was "a very religious man" and a Puritan. Nevertheless he had studied at Montpellier, where the influence of Rabelais, who had been a professor there, must have lingered. Simpson thinks that the story told by Menenius in Coriolanus of the revolt of the body's members against the belly, although originally one of Aesop's fables, had been used by Rabelais and may have come from him through Hall to Shakespeare. He suggests that Shakespeare's doctors in the later plays may have been patterned directly upon Hall, notably the "upright physician" in the sleepwalking scene of Macbeth:

“Certainly no doctor qua doctor appears in the plays until after Hall had arrived in Stratford; and all the doctors in the plays are exemplary characters, entirely worthy members of their noble profession.”

Dr. Caius in The Merry Wives of Windsor is perhaps an exception; but he was French, and from Joan of Arc to the Dauphin Shakespeare's view of the French was the prejudiced one of contemporary Englishmen. (This prejudice need not be extended to his use of the term "French disease" which was common currency everywhere at the time except in France; but even so it may be that a special anti French feeling led him to lean a little more heavily on the term than he might have done otherwise, as we shall see.)