Purpose: Use of complementary and alternative medicine (CAM) is increasing, but some dietary supplements have potentially negative side effects. This study examines CAM and dietary supplement use among a national sample of adolescents. Methods: A total of 1280 adolescents 14-19 years old completed an online survey in 2002 about lifetime and past-30-day use of all CAM modalities, and specifically about use of herbal medicines and dietary supplements. We e-mailed invitations to 12,353 members of Harris Interactive's national Youth Query panel, and filled age/gender quotas sample targets. Data were then weighted to reflect the U.S. adolescent population by gender, race/ethnicity, urbanicity, region, parents' education, propensity to be online, and likelihood of nonresponse. Chi-square and logistic regression analyses were done using SPSS. Results: Seventy-nine percent of adolescents had used CAM in their lifetime, 48.5% in the previous month; 46.2% had used dietary supplements in their lifetime, 29.1% in the previous month; 9.3% reported concurrent use of supplements and prescription medication in the previous month. Factors associated with CAM and supplement use included being female, positive attitudes towards CAM, and being age 16-17 years (rather than in younger or older age groups). Commonly used supplements included ginseng, zinc, echinacea, ginkgo, weight loss supplements, and creatine. Conclusions: Many adolescents use CAM and dietary supplements, including a significant number concurrent with prescription medications. Commonly used supplements (weight loss supplements and creatine) are closely linked to attempts to change body shape. Health care providers should be aware of CAM and supplement use by adolescents.