This paper attempts to give a brief sketch of the Co-Prosperity Sphere during the War period, 1931-45. My conclusions are as follows : (A) The three "bloc economies"-the "Japan-Manchuria Bloc" of the first stage (1931-36), the "Japan-Manchuria-China Bloc" of the second (1937-41), and the "Greater East Asia Co-Prosperity Sphere" of the third stage (1941-45)-were ・disruptively constructed systems. Economic policy and administration of the areas occupied by Japan differed in each period and region. The structure of each region's principal investment institution, its trade relations with Japan, and its. monetary policies underwent necessary changes as regional conditions changed and as the Japanese wartime economy suffered setbacks. (B) The Japanese government used three different types of investment institutions. During the first stage, special state corporations, from which Zaibatsu investment was excluded, were chartered with exclusive rights to develop one industry in one region. In the second stage, three large-scale state policy concerns, with subsidiary companies representing many industries, were established. Zaibatsu as well as government funds were invested in these concerns. In the third stage, the Japanese government designated private companies to develop enterprises in occupied areas. In short, private capital contributed an increasingly large proportion of investment funds. (C) The formation of neither the "Japan-Manchuria Bloc" nor the "Japan-Manchuria-China Bloc" helped Japan's balance of payments. Imports of war materials from the U. S. or Europe could not be substituted for by products from occupied areas. Moreover, the intervention of trade between the S. E. Asian colonies and their former suzerain states by Japan's invation caused economic disaster in those regions. (D) During the first two stages, the Japanese government tried to establish central regional banks and to issue notes linked to the yen. In Manchuria, the monetary system was successfully unified. In China, however, puppet bank notes or Japanese military notes were prevented from circulating widely by strong resistance from fapi (Chinese legal tender) and pienpi (notes in communist liberated areas). The different regional monetary policies caused different rates of inflation in different areas of China. Thus, Japan had to strengthen her restrictions on interregional trade. In the third stage, Japan was unable to establish a central bank to issue yen-linked notes in S. E. Asia. Therefore, she changed monetary policy, and issued military notes equivallent to the currencies circulated in each area. Anticipating explosive inflation, she intercepted remittance relations with these areas. (E) The "Co-Prosperity Sphere", in reality, was disruptive both to interregional trade and to the monetary system. The bloc lacked unity; and, a bloc in name only, was indeed a "Co-Poverty Sphere".