Background: Prayer is a common practice in the United States, yet little is known about the prevalence and patterns of use of prayer for health concerns. Objectives: To determine the prevalence and patterns of use of prayer for health concerns. Methods: We conducted a national survey in 1998 (N = 2055, 60% weighted response rate) on use of prayer. Data were also collected on sociodemographics, use of conventional medicine, and use of complementary and alternative medical therapies. Factors associated with the use of prayer were analyzed using multivariable logistic regression. Results: We found that 35% of respondents used prayer for health concerns; 75% of these prayed for wellness, and 22% prayed for specific medical conditions. Of those praying for specific medical conditions, 69% found prayer very helpful. Factors independently associated with increased use of prayer (P<.05) included age older than 33 years (age 34-53 years: odds ratio [OR], 1.6 [95% confidence interval (CI), 1.3-2.1]; age ≥54 years: OR, 1.5 [95% CI, 1.1-2.0]); female sex (OR, 1.4 [95% CI, 1.1-1.7]); education beyond high school (OR, 1.5 [95% CI, 1.2-1.8]); and having depression, chronic headaches, back and/or neck pain, digestive problems, or allergies. Only 11% of respondents using prayer discussed it with their physicians. Conclusions: An estimated one third of adults used prayer for health concerns in 1998. Most respondents did not discuss prayer with their physicians. Prayer was used frequently for common medical conditions, and users reported high levels of perceived helpfulness.