John Cleland's 1740s pornographic novel, Memoirs of a Woman of Pleasure repeatedly depicts and eroticises the act of defloration. As such it is a revealing illustration of what Ivan Bloch termed the 'defloration mania' of the eighteenth century. This article maps narrative events on to contemporary medical depictions of first intercourse to show the ways that the theories and ideas presented in medical and pseudo-medical texts transferred into erotic fiction and demonstrates how in some instances the bloody defloration scenes can be read as being sex during menstruation, an act which was culturally forbidden at this time.