We have isolated individual P elements from wild-type Q and M' strains in a Korean population (Cheonan) of Drosophila melanogaster by using PCR with inverted repeat primers. Four of the P elements in PCR product were found to be 2.9 kb, 1.15 kb, 0.55 kb and 0.45 kb elements. On the basis of restriction enzyme digest (AvaII/PstI) for the PCR product, 2.9 kb and 1.15 kb elements were confirmed as a complete P element and KP element, respectively. Genomic Southern blot analysis on Q and M' strains were also performed with AvaII restriction enzyme. The result of Southern blot analysis revealed that all of these strains appeared to have a small copy numbers of 2.9 kb complete P element and high copy numbers of 1.15 kb KP element. It might be explained that the reason of the nearly inactive or null for the P factor activity in Korean population of D. melanogaster is probably due to the presence of the highest copy numbers of KP elements which P elements mediated hybrid dysgenesis is suppressed.