Although it has been widely argued that pre-Enlightenment western medicine ascribed to a one-sex (male) model of the body, this theory has never been evaluated in terms of medical practice. This article seeks to determine the usefulness of such a model for early modern Britain, circa 1600–1740, by examining how medical practitioners responded to three common illnesses that aﬄicted both male and female patients: venereal disease, smallpox, and malaria. It concludes that, despite a number of similarities, medical treatment of such illnesses was marked by important differences which were based upon the sex of the patient. Due to its unique physiological functions (vaginal discharge, menstruation, pregnancy, and lactation), the female body was considered by practitioners to be capable of manifesting, transmitting, and responding to disease and treatment in ways that the male body could not. This awareness provided practitioners with additional reasons to monitor, and alter, medical treatment in their female patients. In fact, the different constitutions of men and women meant that the patient body was much more complex than the theory of a one-sex model suggests. Furthermore, differences in medical treatment were influenced by age, a variable which was inexorably linked to physiological changes in the ‘sexed’ body.