From 1987 to 1996, an investigation and study on Lyme disease was conducted in sixty counties and districts of twenty-two provinces (autonomous region, municipality). Seroepidemiological findings indicated that some residents from forest areas of twenty-two provinces had a high antibody titer for Borrelia burgdorferi with positive rate 5.06% (1724/34104). Endemic foci of Lyme disease were discovered in seventeen provinces by etiological evidence. Typical cases of Lyme disease were diagnosed in eleven provinces. Prevalence rate of Lyme disease in forest region of northeast China was 1%-4%. Ixodes persulcatus played a leading role in the transmission of Borrelia burgdorferi to human in northern part of China. Ixodes granulatus and Haemaphysalis bispinosa might serve as principal vector of Borrelia burgdorferi in the southern region. Genus apodemus might serve as a major reservoir for B. burgdorferi. A total number of 130 isolates of B. burgdorferi were recovered from patients, ticks or animals. Isolates from China were obviously different from the ones isolated in North America in SDS-PAGE protein profile, plasmid and REA. The analysis of rRNA gene restriction patterns indicated that the Chinese isolates were divided in three genospecies. Genospecies I (B. burgdorferi sensu stricto) was firstly discovered in Asia.