The development of menstrual regulation has forced us to look anew at the legal and medical distinctions between various methods of fertility control. The once clear difference between contraception and abortion blurs. The distinction had already been complicated by development of the pill and the IUD. While it seems clear that some forms of the pill function as contraceptives, actually preventing fertilization, the IUD apparently does not. The IUD instead prevents the implantation of the fertilized ovum in the uterus, as does the so-called "morning after" pill, which came into use in the mid-1960s. Although several authors have argued that both methods violate criminal abortion statutes,' there is no evidence that any successful criminal abortion prosecutions have ever been brought on that theory. Despite some lingering doubts, these methods are now considered "contraceptives" for several reasons: First, it is impossible to show that they function technically as abortifacients because they are effective so soon after a supposed conception. Second, the time-honored notion that pregnancy begins at fertilization has been eroded by recent changes in professional opinion.2 It is not improbable, then, that menstrual regulation will either be looked on as "contraception" or placed in a special category somewhere between contraceptives and abortifacients and referred to simply as a postconceptive fertility control method. Whether this will happen depends in large measure on the interpretations given to contemporary abortion legislation. Past experience and present ambiguities raise a number of questions as to the legal status of menstrual regulation: Is it likely to be prohibited by the criminal abortion statutes now in force in many countries? Can medical intervention be classified as abortion in the absence of proof of a preexisting pregnancy? What effect do the specific requirements of abortion statutes have on menstrual regulation? Beyond that, will it be possible to classify MR technology as contraceptive rather than abortifacient? And will MR be permitted because it can be used for medical purposes other than abortion? Finally, will the procedure lead to reappraisals of the legal notion of abortion? The aim of this article is to explore these questions. Legislation dealing with abortion is necessarily the touchstone for our analysis.