This paper identifies the major factors explaining GDP growth in a number of Southeast Asian countries during the 1980s and early 90s. Estimates of the contribution of technological change, increases in the endowments of labor and capital, movements in the terms of trade, and changes in domestic output prices are reported for Hong Kong, Japan, South Korea, the Philippines, and Thailand. Partial results for Indonesia and Malaysia are also shown. An index number approach is used; it has a tight theoretical foundation, being based on the GNP/GDP function approach to modeling the production sector of an open economy.