Malaria was steadily decreasing in Korea except in certain counties of the mountainous and hilly areas, in the 1960s. Judging from the present epidemiological, social and economic conditions, it can be said with confidence that malaria with "unstable" characteristic in the Republic of Korea has already been disappeared. No doubt, the causes of the disappearance of malaria are complex. Certainly improved living conditions and life style; better medical and educational facilities in the wake of a rapid economic development could all have some role. On the other hand, the disappearance of malaria without large scale control operations could be ascribed to the two main factors: one is malaria case detection and simultaneous drug therapy available through the nation-wide passive case detection network during the 1960s and the other is rapidly improved farming practices begun in 1970s, which resulted in the use of a huge quantity of pesticides and other chemicals for agriculture, which, in turn, might affect local anopheline vectors which were originally not effective ones any way.