The systematic review to identify the studies presented in the Handbooks and summarized in this paper was conducted as follows. We utilized a combination of strategies to identify the studies (excluding most reviews or qualitative research). First, we systematically searched online databases (PsycINFO, MEDLINE, etc.) using the search words “religion,” “religiosity,” “religiousness,” and “spirituality” to identify studies on the R/S-health relationship. Second, we asked prominent researchers in the field to alert us to published research they knew about and to send us research that they themselves had conducted. Third, if there were studies cited in the reference lists of the studies located, we tracked down those as well. Using this method, we identified over 1,200 quantitative original data-based publications during the period 1872 to 2000 and 2,100 studies examining the R/S-health relationship from 2000 to 2010. All of these studies are described in the appendices of the two editions of the Handbook. Based on other reviews of the research conducted around this same time period (but more limited), we estimate that our review captured about 75% of the published research. Bear in mind that many, many more qualitative studies have been published on the topic that were not included in this review.