Since pine wilt disease was first reported in Busan in 1988, this disease has become a serious threat to pine forests in Korea. A general survey for Bursaphelenchus xylophilus group (B. xylophilus, B. mucronatus) nematodes were carried out to determine their geographic range, host tree species and insect vectors, Monochamus species. Based on the survey results, B. xylophilus were found over 57 cities or district and a similar nematode, B. mucronatus also has been isolated over 30 cities or district including Jeju and Pocheon. The Asian type of B. mucronatus was founded from Pinus thunbergii and P. densiflora, generally associated with M. alternatus as its insect vector. The European type of B. mucronatus which was limited distribution to the central areas, such as Yeongwol, Bonghwa, Yeongdeok, was also found on P. koraiensis and P. desiflora associated with M. saltuarius. Both Monochamus species transmitted both Bursaphelenchus species and co-existed in Muju and Yeongdeok predicted as their range margin. Their range margins shifted northwards compared to 2006, seemingly as a result of climate change. Recently, the European type of B. mucronatus has been identified in other several areas since it was first reported in Pocheon in 2008. Several reports indicate the potential pathogenicity of European type of B. mucronatus and other species, B. sexdentati and B. lenoni in Europe. Therefore, sustainable survey and the study for the newly invading Bursaphelenchus species as well as the member of B. xylophilus group should be performed to protect Korean forests.