Lyme disease is currently the most frequently reported vector-borne illness in the United States, accounting for more than 95% of such cases. The purpose of this report is to provide recommendations for preventing Lyme disease, including the use of Lyme disease vaccine. Individuals can reduce their risk of Lyme disease by avoiding tick-infested habitats when in endemic areas. If exposure to tick-infested habitats cannot be avoided, individuals may reduce their risk of infection by using repellents, wearing protective clothing, and regularly checking for and removing attached ticks. Morbidity from Lyme disease can be reduced significantly by detecting and treating the infection in its early stages; early and appropriate treatment almost always results in a prompt and uncomplicated cure. A Lyme disease vaccine (LYMErix, SmithKline Beecham, Collegeville, PA) was licensed by the US Food and Drug Administration on December 21, 1998, for persons 15 to 70 years of age. This vaccine seems to be safe and effective, but whether its use is cost-effective has yet to be clearly established. Use of this vaccine causes false-positive enzyme immunoassay results for Lyme disease. Lyme disease can be diagnosed in vaccinated persons by immunoblot testing. Decisions about the use of this vaccine should be based on an assessment of a person's risk as determined by activities and behaviors relating to tick exposure in endemic areas. This vaccine should be considered an adjunct to, not a replacement for, the practice of personal protective measures against tick exposure and the early diagnosis and treatment of Lyme disease.