OBJECTIVES:  A dietary supplement (DS) is defined as “any product intended for ingestion as a supplement to the diet.” These substances include vitamins, minerals, herbs, amino acids, and other substances.  Marketing data show a dramatic increase in DS sales in the last decade. The most recent published literature on the prevalence of DS use in United States was based on data from 1999-2000. There is a need for updated literature. The objective of this study was to measure the prevalence of DS use and to examine associations of its use with select demographic characteristics in the United States. METHODS:  DS data from 2007–2009 National Health and Nutrition Examination Survey (NHANES), a nationally representative, cross-sectional survey of US health and nutrition, was analyzed. The proportions of users of any DS, multivitamins/multiminerals, vitamin-B-complex, calcium, calcium/antacids were calculated. Bivariate and Multivariate analyses were done to assess the relationship of DS use and some demographic/lifestyle characteristics. RESULTS: Approximately 43% of US population reported taking DS(s) in the past month; DSs were consumed by females (48%) more than males (38%), youngers (0-11 years; 33%) and elders (40 years and more; 59%) more than middle age (12-39 years; 29%), more than high school educated people (56%) than less than high school (30%), non-Hispanic Whites (50%) more than other races (average 30%). Multivitamins/multiminerals were the most commonly consumed DS (60%) followed by antacid, vitamin B-complex and vitamin C. In bivariate analyses non-Hispanic White race, older age categories, more education, and female gender were significantly associated with greater use of any DS. In multivariable analysis the latter three characteristics were still associated with greater use. CONCLUSIONS: A substantial proportion of the US population takes DS mainly as vitamins, minerals, and/or other dietary supplements. This study provides detailed information for health care professionals and researchers regarding the DS use.