Lyme disease, presently the most common arthropod-borne disease in the United States, is a phenomenon of both medical and social importance. Notwithstanding the substantial public health threat posed by Borrelia burgdorferi infection, there is reason to suspect that the diagnosis of Lyme disease is made more frequently than justified. On the other hand, the current dissatisfaction with serologic assays for B. burgdorferi infection may lead some physicians to inappropriately abandon consideration of the diagnosis entirely. Either of these outcomes of the patient-physician encounter is to be regretted. The Lyme disease problem, as I call the current situation, has both biological and social determinants.