Between January 1984 and December 1989, 102 indigenous cases of Lyme disease were reported in North Carolina. Lyme disease was reported in each of the three major geographic regions of the state: mountain, piedmont, and coastal plain. One or more diagnoses were made in 42 of 100 counties. Patients ranged in age from 5 months to 78 years (median, 27 years); 58 patients (57%) reported a history of tick exposure within 1 month of the onset of symptoms. Erythema migrans was reported by 93 patients (91%). Arthritis (30%), neurologic symptoms (10%), and cardiac abnormalities (7%) were observed. Thirty of the 102 cases were confirmed serologically by indirect fluorescence microscopy or enzyme-linked immunosorbent assay.