We examined dietary supplement use for weight loss and perceptions about safety, efficacy, and regulatory oversight of these products. A random digit-dialed telephone survey was conducted in 2005-2006, with a representative sample of 3,500 US adults. The survey assessed the beliefs and practices related to weight control. Outcome measures included the prevalence of dietary supplement use for weight reduction, demographic profile of supplement users, and knowledge about safety, efficacy, and regulation of dietary supplements. Of the adults who made a serious weight-loss attempt (n = 1,444), 33.9% reported ever using a dietary supplement for weight loss. Supplement use was more common among women (44.9%) vs. men (19.8%); those aged 25-34; African Americans (48.7%) or Hispanics (41.6%) vs. whites (31.2%); less educated (38.4% high school degree or less vs. 31.1% some college or more); lower income households (41.8% made <$40K vs. 30.3% made > or =$40K); obese (40.7%) vs. overweight (29.1%); those who made more lifetime weight-loss attempts (42.0% made > or =3 vs. 22.1% made <3); and those who used more weight-loss methods (48.2% used > or =4 vs. 25.2% used <4). Many users and non-users of dietary supplements had misperceptions about these products-many believed they are evaluated for safety and efficacy by the Food and Drug Administration (FDA) before marketing, and that dietary supplements are safer than over-the-counter (OTC) or prescription medications. Use of dietary supplements for weight loss is common. More information about dietary supplements is necessary to correct misperceptions and encourage the use of safe and effective weight-loss methods.