Lyme disease (LD) is caused by the tickborne spirochete Borrelia burgdorferi sensu lato and is the most common vectorborne disease in the United States. Surveillance for LD was initiated by CDC in 1982, and the Council of State and Territorial Epidemiologists designated it a nationally notifiable disease in January 1991. For surveillance purposes, LD is defined as the presence of an erythema migrans rash > or =5 cm in diameter or laboratory confirmation of infection with evidence of at least one manifestation of musculoskeletal, neurologic, or cardiovascular disease (1). This report summarizes the provisional number of cases of LD reported to CDC during 1996 and indicates that the number of cases reported to CDC was a record high.