In first-world countries the popular autobiography of assisted reproduction organizes itself largely around the paradigm of childless marriage, which most of the world regards as a social problem, or at least as a social disvalue. Biotechnology enters the equation when culture transmutes childlessness into infertility, a disease to which one can apply medical therapy. 2 Reproductive technologies rarely cure the “illness,” which affects 8% to 12% of heterosexual couples worldwide (Inhorn, 2003a, 1837), but they often provide a way around the symptoms, enabling wives to conceive and bear children. Hence the stereotypical, sympathetic American portrait of infertility patients: loving, otherwise healthy, childless (or childless but for the intervention of reproductive technology), white, economically stable, married women and men. We introduce our topic with a discussion of the significance of recent debates over nature and kinship for evaluation of ARTs. We articulate our own method and introduce the technologies that give rise to the questions. We then turn to an extensive discussion of the “natures” that ARTs enforce or transgress, paying close attention to the way in which religious belief—taking shape in a particular political, economic, and communal setting—affects these judgments about naturalness. We explore ideas of the natural family and the place of marriage and childbearing that they entail; we analyze reactions to third-party involvement in family-formation through adoption, gamete donation, and surrogacy; we discuss ideas about the nature and status of unused embryos; we examine ideas about natural gender roles and identities and the ways in which infertility and ARTs erode or preserve them; we examine the normative status of the so-called new families ARTs make possible: genetically connected gay and lesbian partnered families, and intentionally single motherhood; we analyze intercourse and conception as a single or divisible natural process; and we reflect briefly on the “naturalness” of using ARTs to select for or against disease, gender, or traits. Then we step back from these distinct but related issues to ask two larger questions. First, how does pronatalism of various kinds interact with a specific set of religious beliefs and practices in a particular cultural setting, and what are the sometimes surprising practical consequences of this interaction? Second, how do religious people incorporate the idea of ARTs into their functional religious universes, whether they ultimately accept or reject them? How must they alter their understandings of authority, power, law, divine will, or the cosmos in order to accept ARTs as natural? We close with recommendations that policymakers pay attention to religious people, and not merely to religious statements and religious leaders, if they desire an accurate understanding of religious people’s responses to ARTs and also of the pressing social issues ARTs raise but that religious discussions of them often ignore.