There has been little data on the prevalence of supplement use and the characteristics of the dietary supplement users in the Republic of Korea. This study presents the prevalence and the details of any dietary supplement use and the characteristics of the adults who use dietary supplements in the Republic of Korea. Between May 18 and June 16, 2006, nationwide and population-weighted personal interviews with 6,201 adult aged from 30 to 69 years were conducted and the final sample consisted of 3,000 people with a 49.8% response rate. We examined the prevalence and details of the use of dietary supplements and the characteristics of those who use the dietary supplement among adults. About sixty two percent of adults had taken any dietary supplement during the previous 12-month period in 2006. The most commonly reported dietary supplement was ginseng, followed by multivitamins, glucosamine, probiotics, and vitamin C. Female (versus male), an older age group, a higher family income, those living in metropolitan cities, those with marital experience, those with a higher level of education, and those having medical problems had a greater likelihood of reporting the use of any dietary supplements. The particular relationships differed depending on the type of supplement. The most Korean adults took one more dietary supplement and the dietary supplement users had different demographic and health characteristics compared to those of the nonusers. Research on diet supplements by the medical community is needed in the future.