The secularization debate is widened from the Christian context to include the case of Judaism. Certain characteristics of Judaism, the integral ethnic-religion link and the focus on practice, are expected to mediate the effects of modernity on religion among Jews. Data on patterns of religiosity are presented within a framework of a secularization thesis, emphasizing the ethnic and national basis of contemporary patterns. Four antisecularization arguments are evaluated: a change in Jewish religiosity from practice to beliefs and ethics; the development of a Jewish civil religion with its own sacred beliefs and practices; the search among Jews for supernatural compensators outside Judaism; and a revival of traditional Jewish religious practices among the fourth generation. The evidence points to two divergent changes, both of which are related to modernity: a stabilization of religious practice among the majority and a more stringent pattern of religious practice among a growing minority.