A survey on rats and rat-fleas was performed in costal area of Korea during 1972 in Inchon, Kunsan, Yosu, Busan and other areas. The number of the caught rats was 1,448. Total number of collected fleas was 2,480. Geographical distribution were described. Flea index was in 1.71 total. Mothly flea indices were 0.35-0.84 in January to March, 2.13-2.59 in April to June, 0.58 in July and 1.82-4.91 in August to November. Mortality rate of X. cheopsis to various concentration of DDT in 1 hour exposure were 43.8 % in 4.0 %, 30.4 % in 1.0 %. In 24 hours exposure, the mortalities were 100 % in 4.0 %, 91.5 % in 2.0 %, 73.5 % in 1.0 % and 37.0 % in 0.5 % DDT.
