In the globalization discourse, Christianity and Islam are often construed as representing two traditions that are conflicted and incompatible. This study engages the "clash of civilizations" discourse by examining MuslimChristian differentials in the use of modern contraception in Nigeria, where Christians have a much higher contraceptive prevalence, and Tanzania, where Muslims are somewhat more likely to use contraception. Employing data from six nationally representative surveys conducted in the two countries between 1990 and 2004 and multilevel logistic regression, we find that the effects of religion remain strong but operate largely through the community religious milieu. Contraceptive use tends to be highest in religiously mixed areas, but the "optimal" religious makeup differs between the two nations, reflecting the historically shaped configurations of their religious expressions and politics.Fueled by politics, the issue of the "civilizational" opposition of Christianity and Islam frequently, even if not always explicitly, makes its way into current globalization discourse. Drawing upon various dimensions and aspects of Christianity's and Islam's historical patrimony and present-day realities, elaborate and forceful arguments are made that reify a gulf dividing the two "civilizations" and, on the contrary, reduce the differences between Christian and Muslim heritages and politicocultural expressions to mere miscommunication or opportunistic manipulations (e.g.One of the most commonly used yardsticks to assess the differences between the Christian and Muslim worlds is their receptivity to cultural and technological changes. It is often presumed that the former possesses better aptitude and flexibility to embrace and internalize innovations than the latter. These and similar assumptions and assessments, however, seldom rest on a thorough examination of empirical data-mainly because appropriate and well-measured indicators of such innovations are rare. In this study, we look at contraceptive use in the context of high fertility-a sort of novel cultural technology that can be easily measured without bias. We focus on what is often labeled "modern" contraceptives-hormonal or barrier methods that are scientifically developed and industrially produced, whose invention and spread are historically recent and whose practical purposes and cultural load are often very different from "traditional" methods of birth control. Importantly, in the settings that we examine here contraceptives are usually available free of charge or are heavily subsidized, which effectively eliminates the pecuniary barriers that often hinder the spread of other novel technologies.The last half-century has witnessed a global contraceptive revolution. This revolution, however, has not impacted the world evenly. sub-Saharan Africa remains one of the last "family Acknowledgments: The authors are thankful to Cecilia Menjívar, S. Philip Morgan, and Jenny Trinitapoli for useful comments and suggestions. Correspondence should be addressed to Victo...