Bursaphelenchus xylophilus is causal agent of the pine wilt disease, one of the major conifer diseases worldwide. This nematode is a quarantine organism in the European Union, where it has recently been discovered in a restricted area in Portugal. In our laboratory, research has been developed to characterize the genetic diversity of the nematode, and to provide a more comprehensive view of the relationships between B. xylophilus and the non-pathogenic Bursaphelenchus species. For that purpose, repetitive sequences known as satellite DNA (satDNA) have been cloned and characterized from the genome of B. xylophilus. Its species-specific distribution and high copy number in the genome make this sequence a very promising tool for molecular identification of the nematode, as will be illustrated with results obtained in the laboratory. In particular, the recent development of a very sensitive satDNA based real-time PCR assay will be presented. Moreover, sequencing of monomers of the satDNA was performed and phylogenetic analyses were conducted to analyse the diversity and relationships (1) between B. xylophilus isolates sampled worldwide; (2) among B. xylophilus populations all collected in the infested area from Portugal. Results will be discussed in the context of the origin and evolution of the pine wood nematode complex in Europe.