In Western Europe, “religious sociology” developed after the Second World War and, in order to improve its theory and methods, the Société International de Sociologie Religieuse (SISR) was established in 1948. After comparing its aims with those of the American associations, the author discusses the reception of religious sociology by the churches in Europe. The churches were interested in the description and analyses of the social context in which they were embedded, but they rejected the analyses of religion per se. This ambiguous relationship can also be traced in the development of the SISR, where over the years a “sociology of religion” developed. To explain this change, the author stresses, among other factors, the important impact of the interactions between European and American sociologists of religion during the conferences organized by professional associations. The profession and not the churches became the reference of a new generation of sociologists. Religion rather than the churches became the focus of study, which restored our discipline to mainstream sociology. In a concluding section, new tasks for the professional organizations are suggested and the need for intercontinental research projects is stressed.