De specialibus legibus 3.34-36 is one of the more intriguing passages in which Philo deals, in one way or another, with sex. Here in the Exposition of the Law, Philo considers the phenomenon of infertile marriage. More specifically, he addresses two different cases of infertile marriage, and offers contrasting assessments of each. The passage is of particular interest for two reasons. First, unlike the surrounding material, Philo has no scriptural basis for his interpretation in this section. Second, in one of the two cases addressed, Philo offers what seems to be qualified approval of the childless marriage as a going concern but does not specify sexual abstinence for partners who, on the face of it, cannot engage in procreative intercourse. This silence appears particularly pointed when viewed against the immediately preceding section and in light of Philo's perspective on sex more generally. In Spec. 3.32-33, Philo unambiguously prohibits sexual activity for the duration of another situation not conducive to procreation, the time of a woman's monthly period. More generally, Philo's perspective on sex is notoriously demanding. In a wide range of passages across the Philonic corpus, Philo presents a strict procreationist perspective that, it would seem, finds no legitimate place for nonprocreative (marital) sex. This paper has three goals. First, it locates and considers Spec. 3.34-36 alongside other sections of Philo's treatment of the Sixth [/Seventh] Commandment, sections with which it shares a conspicuous characteristic: the rationalization of the biblical legislation in the conceptualization of illicit sexual activity as a condemnable wasting of seed. Second, it explores the phenomenon of the inclusion of this passage in Philo's presentation of biblical law. Why does Philo include this material? Third, it addresses the particular puzzle identified above. What should we make of Philo's failure to specify sexual abstinence in Spec. 3.35? If, implicitly, Philo does allow for ongoing sexual activity within some marriages long since proved infertile, why or on what basis might he do this? In response to this question, the paper interacts with the reading of Spec. 3.34-36 proposed by Maren Niehoff (in her influential study, Philo on Jewish Identity and Culture), who finds in this passage support for her contention that Philo's procreative concern is directed towards the wider context or general framework within which sex occurs, rather than sexual activity per se. In response, this paper argues that if Philo sanctions ongoing sexual activity in the case of certain infertile marriages, and that without fatally compromising his procreationist convictions, the outstanding candidate for satisfaction of the procreative requirement is the procreative intention of the husband. The paper concludes with some brief reflections on the challenge of framing Philo's perspective on marriage and sexual conduct, and, correspondingly, of accounting for certain details in Philo's treatment of marriage and sexual conduct that seemingly jar with his central convictions.