SummaryThe Japanese economy is now the second largest market economy, with a large trade surplus. And yet, Japan's imports of manufactures have long been very low relative to its GNP, when compared with other industrial countries; its ratio of manufactured imports to GNP was in the range of 2.1–2.7% in the 1980‐87 period, as compared with 8.5–10.3% for the industrial countries as a whole or 4.7‐7.2% for the United States. The share of developing economies in total imports of manufactures in Japan is about the same as, if not higher than, those for most other industrial countries. If Japan's ratio of manufactured imports to GNP were to rise in the future to approach closer to those of other industrial countries, Japan's imports of manufactures from developing economies could be two to three times what they are today, even if Japan's GNP does not increase at all and the share of developing economies in Japan's manufactured imports does not increase.This paper is an attempt to probe the potential of the Japanese market for imports of manufactures from developing economies in terms of rising ratio of such imports to GNP. The paper explores the reasons why Japan's ratio is exceptionally low, on the basis of existing literature.(a) Japan's ratio of manufactured imports to GNP has remained exceptionally low compared with those for other industrial countries.(b) Japan's ratio of manufactured imports from developing economies to GNP has remained distinctly low despite the recent surge in such imports.(c) If a part of the reason for the low ratio for Japan was a market access problem as often alleged, the problem is not with formal import barriers such as tariffs and formal non‐tariff barriers because these barriers in Japan are no higher than in other industrial countries.As for informal import barriers, evidence found indicates that:(i) Administrative guidance and flexibly managed competition policy, which in the past had considerable effects of limiting imports, appear to have declined‐in importance, but they still have import‐limiting effects in certain areas.(ii) Market access difficulties involving import procedures, product standards, testing and certification requirements, which were enormous in the past, may have also decreased in severity over the last decade, but problems in these areas persist.(iii) There are aspects of the Japanese distribution system and practice that seem to make foreign access to the Japanese market significantly more difficult than the access by Japanese exporters to the markets in other industrial countries. Distribution in Japan suffers from overregulation.(iv) Users of manufactured products in Japan are sensitive to quality, perhaps more so, on the average, than in other industrial countries.Does the recent upsurge in Japan's imports of manufactures suggest that the traditional import behavior of Japan is changing? Japan's manufactured imports measured in yen increased by 18 and 27 percent in 1987 and 1988, respectively, and those coming from developing economies increased even more rapidly. There is also some evidence that price and income elasticities of demand for manufactured imports may have increased recently. These are encouraging, but it remains to be seen whether the trends will continue far enough into the future to bring Japan's import behavior more into line with those of other industrial countries. If they do, implications for the market prospects of manufactured exports from developing economies could be far‐reaching.Outstanding questions are:(i) How much of the recent increase in manufactured imports is attributable to the appreciation of the yen (price effect)? How much is attributable to the increase in income or industrial output (income effect)? How much is attributable to removal of formal and informal import barriers effected so far (structural change)? Has consumer taste changed?(ii) Why have Latin American countries not been successful in promoting their exports of manufactures to Japan, when Asian exporters have been so successful?(iii) Up until now, the share of developing economies in Japan's manufactured imports has not been particularly low compared with those for other industrial countries, but is this share likely to fall or rise in the future?(iv) What is the likely impact of recently increased direct investment (DFI) by Japanese manufacturers in developing economies on the imports of their prod