Chapter 4, Obscene… in a Certain Sense, shows how charges of obscenity were used against pornographers and irregulars during the 1850s and 1860s, amid landmark changes to obscenity law. In doing so, it introduces one of the book’s major arguments: that allegations of medical obscenity were usually tactical, and became increasingly imbricated in projects aimed at contesting medical authority. The most influential anti-vice group of the period, the Society for the Suppression of Vice, led a crackdown on the pornography trade during this period, which brought medical works into the courtroom, and some were destroyed on the grounds that they were obscene. The chapter parallels arguments that medical works could be obscene in court with tactics in the medical press. With mixed success, campaigns against “obscene quackery” attacked irregular practitioners who treated sexual issues by arguing that their manuals’ low prices and wide circulation made them a threat to public morals. The chapter ends with the 1868 formulation of the Hicklin test, a legal test of obscenity that affirmed that arguments examined in this chapter could justify the destruction of medical works.