More than nine million Muslims currently live in Western Europe, which makes them the largest religious minority in the region. There has been significant political controversy in various European states over how best to recognize Muslims' religious rights. These questions have become even more significant and contentious in the aftermath of the September 11 attacks by Islamic extremists. Using privately commissioned polls on attitudes toward Muslim religious rights taken before and after September 11 in Britain, France, and Germany, this article determines the extent of popular opposition to state accommodation of Muslim practices and tests several leading theories of attitudes toward Muslims. We conclude that the most important determinants of attitudes toward Muslims are education and religious practice.