This article attempts to make progress on both the problems of sexually transmitted disease and acquaintance rape by proposing a new crime of reckless sexual conduct. A defendant would be guilty of reckless sexual conduct if, in a first sexual encounter with another particular person, the defendant had sexual intercourse without using a condom. Consent to unprotected intercourse would be an affirmative defense, to be established by the defendant with a preponderance of the evidence. As an empirical matter, first-encounter unprotected sex greatly increases the epidemiological force of sexually transmitted disease and a substantial proportion of acquaintance rape occurs in unprotected first encounters. The new law, by increasing condom use and the quality of communication in first sexual encounters, can reduce the spread of sexually transmitted disease and decrease the incidence of acquaintance rape.