Individuals in the following categories may be eligible for this study: chronic Lyme disease; chronic Lyme arthritis; seropositive control (are infected with the bacteria that causes Lyme disease but do not have disease symptoms); recovered control (have been sick with Lyme disease but were treated successfully and are currently well); control with multiple sclerosis (patients with multiple sclerosis); and healthy volunteers. Patients in the chronic Lyme disease category must be age 13 and above; all others must be age18 and above. Candidates will be screened with blood and urine tests.