The purpose of this book is to examine the accepted concepts and theories on surplus labor in underdeveloped agricultural economics, particularly in the literature on "disguised unemployment." By doing so, the author clears tha way toward finding a more valid theoretical concept of this vital subject, which is the core of potential economic and social development in the underdeveloped countries. The author, after establishing a more realistic and workable definition of surplus labor on the basis of a closer investigation of the extended family-clan-village system, so typical of the tradition-guided underdeveloped societies, proceeds to work out a method for measuring true surplus labor, with rural South Korea as a case example. Of particular interest is the author's distinction between two types of surplus labor: technical (open) idle labor and the tradition-directed (closed) idle labor. Thus having obtained quantitative data on the extent of underemployment in South Korea, the author continues with a discussion of policy implications in the employment structure of underdeveloped countries, and constructs a proposed program for the utilization of surplus labor, without the application of totalitarian methods, without waiting for the availability of additional capital from the outside, and without making a change in traditional instituions and a priori condition for the utilization of idle labor. This program calls for capital improvements within the agricultural area, financed by the agricultural sector itself, after it is shown through statistical data that capital improvements in agriculture yield quicker and greater results than in other sectors of the economy. The author also attempts to show how such a program would not only put to work a major part of unutilized labor on agricultural development projects, but would also pave the way toward a gradual dissolution of those social traditions and institutions that have been economically hampering and that have been, thereby, an important cause of perpetuating economic and social stagnation. The author also claims for his program the aded virtue of minimizing the social unrest that results from economic distress, thus safeguarding political stability within the framework of needed reform. The government of the Republic of Korea cooperated closely with the author in carrying out the research underlying this study. Basic statistical data were obtained through the cooperation of the research department of the Bank of Korea. The purpose of this book is to examine the accepted concepts and theories on surplus labor in underdeveloped agricultural economics, particularly in the literature on "disguised unemployment." By doing so, the author clears tha way toward finding a more v