Isofemale lines of the Taeneung D. melanogaster were analysed for polymorphisms of P element by in situ and Southern hybridization techniques. Biotin-labeled 4.7 kb BamHI and 0.7 kb PstI fragments of pπ 25.1 containing complete P element were used as probe DNA. In situ hybridization with BamHI probe of 200 isofemale lines at generation 4 revealed that all the strains tested contained as many hybridization sites as the US P strain Harwich. The average copy numbers per genome were 45.23±4.93, and X chromosomes had higher frequencies of P elements than autosomes (X > 3R > 2R > 3L > 2L). In hybridization with PstI probe, the copy numbers per genome were reduced drastically to 4.48±1.64. In Southern blot analysis of genomic DNAs isolated from 50 isofemale lines (15 Q and 35 M strains), all strains showed more than 30 copies of DNA sequencies homologous to BamHI probe, although the hybridization patterns differed from strain to strain. The copy numbers of central-portion-retaining P element detected by PstI were consistently much smaller compared to those observed by the BamHI and were different among strains. The Q strains had in general higher copy numbers (average/genome: 4.73±2.02) compared to the M strains (2.71±1.20). These results indicate that a great majority of the P elements existed in the Taeneung population were defective type.