For the purpose of identifying DNA repair-related genes in D. melanogaster, a wide variety of mutants have been produced by use of P-element. Of them 4 UV-sensitive lines have been selected through a set of screening methods. Several kinds of genetic studies involving UV-sensitivity tests, recombination frequency analyses (female), and insertion site determination by molecular techniques related as well as male recombination tests (MRT), have been performed. These lines (called PUS lines) showed somewhat different recombination rates from those of the normal lines which do not have P-element inserted. Moreover, chromosome walking using the very P-tagged genes is being carried out. The results so far obtained are as follows: the insertion sites of P in each PUS line are 3rd chromosome (PUS # 25, # 248), and X-chromosome (# 92, # 181). The relative UV-sensitivity of each line is 0.734 (# 25), 0.780 ( # 92), 0.860 (# 181), and 0.611 (# 248), respectively. Especially, one of the intriguing features of PUS # 25 is that its male recombination has occurred (approximately 0.14%). In addition, recombination rates(female) obtained were somewhat higher than those of the control groups, by 7.1% (# 25), 3.46% (# 92), and 6.09%. (# 181), respectively.