Jewish tradition is focused much more on religious practice than on religious belief, whereas various denominations of Christianity focus about equally on religious practice and on faith. We explored whether this difference in dogma affects how Jews and Protestants judge religiosity. In Study 1, we showed that Jews and Protestants rated practice equally important in being religious, while Protestants rated belief more important than did Jews. In Study 2, Jewish participants' self-rated religiosity was predicted by their extent of practice but not knowledge of Judaism or religious beliefs. In contrast, in Study 3, Protestants' self-rated religiosity was predicted both by their extent of practice and belief, but not knowledge. In all, the results show that Jews and Protestants view the importance of practice in being religious similarly, but that belief is more important for Protestants. Copyright © 2002 John Wiley & Sons, Ltd.