The document summarizes the Heckscher-Ohlin (H-O) theory of international trade. The H-O theory states that countries will export goods that use their abundant and cheap factors of production intensively and import goods that use their scarce factors intensively. It assumes countries differ in their endowments of capital and labor. The theory shows that capital-abundant countries will export and produce capital-intensive goods, while labor-abundant countries will export and produce labor-intensive goods. The theory represents an improvement over previous theories in explaining the basis of trade between countries within a general equilibrium framework.