The phenomenon of segregation-distorter (SD) has now been detected in natural population of D. melanogaster from Chunnam, Korea. The genetic backgrounds of this SD (SD-kor) were examined and the followings were found: 1. Males heterozygous for SD-kor chromosome and a cn bw chromosome show mean k value of 0.995. 2. The frequency of the SD in the Korean populations of D. melanogaster is low (0.68%). 3. Segregation-distortion is not expressed in the heterozygous females (mean k value of 0.510). 4. The SD-kor action is inhibited by the Curly inversion. 5. The SD-kor chromosome carries the recessive lethal genes. 6. The SD-kor is not sensitive to the original-SD strains tested.