The investigation of Lyme disease in Beijing area is reported for the first time. The sera of 1314 local residents were examined by indirect immunofluorescent assay. 11.9% of them were seropositive to Borrelia burgdorferi. The principal vector was Haemapsysalis longicornis. Six strains of B. burgdorferi were isolated from ticks or patients using modified BSK medium. Spirochetes were found in 5 of 30 patients' skin biopsy samples. Penicillin or ceftriaxone was used to treat the patients, and the effective rates were 64% and 88%, respectively.