Religion's effects on mental health have been debated for years, yet only in the last half century have these theories been empirically tested. While a number of mental health constructs have been linked to religion, one of the most prevalent and debilitating mental health indices, anxiety, has been largely ignored. This paper categorizes and critically reviews the current literature on religion and general indices of anxiety in terms of findings linking decreased anxiety to religiosity, increased anxiety to religiosity, and those finding no relation between anxiety and religiosity. Results from 17 studies are described and synthesized. Conceptual and methodological weaknesses that potentially threaten the validity and generalizability of the findings are discussed. Finally, conclusions and directions for future research are provided.