BACKGROUND: Some patients with medically unexplained symptoms or alternative medical diagnoses suspect that they chronically suffer from the tick-borne infection Lyme disease. These patients are commonly targeted by providers of alternative therapies. This study was designed to identify and characterize the range of unorthodox alternative therapies advertised to patients with a diagnosis of Lyme disease. METHODS: Internet searches using the Google search engine were performed to identify the websites of clinics and services that marketed nonantimicrobial therapies for Lyme disease. We subsequently used the PubMed search engine to identify any scientific studies evaluating such treatments for Lyme disease. Websites were included in our review so long as they advertised a commercial, nonantimicrobial product or service that specifically mentioned utility for Lyme disease. Websites with patient testimonials (such as discussion groups) were excluded unless the testimonial appeared as marketing on a commercial site. RESULTS: More than 30 alternative treatments were identified, which fell into several broad categories: these included oxygen and reactive oxygen therapy; energy and radiation-based therapies; nutritional therapy; chelation and heavy metal therapy; and biological and pharmacological therapies ranging from certain medications without recognized therapeutic effects on Borrelia burgdorgeri to stem cell transplantation. Review of the medical literature did not substantiate efficacy or, in most cases, any rationale for the advertised treatments. CONCLUSIONS: Providers of alternative therapies commonly target patients who believe they have Lyme disease. The efficacy of these unconventional treatments for Lyme disease is not supported by scientific evidence, and in many cases they are potentially harmful.