Using data from the 2002 National Survey of Family Growth, we show that women who report that religion is "very important" in their everyday life have both higher fertility and higher intended fertility than those saying religion is "somewhat important" or "not important." Factors such as unwanted fertility, age at childbearing or degree of fertility postponement seem not to contribute to religiosity differentials in fertility. This answer prompts more fundamental questions: what is the nature of this greater religiosity? And why do the more religious want more children? We show that those saying religion is more important have more traditional gender and family attitudes and that these attitudinal differences account for a substantial part of the fertility differential. We speculate regarding other contributing causes.