The book addresses the empirical validity of the factor proportions theory based on a new, extensive data basis. Departing from Heckscher-Ohlin theory, it extends existing models by allowing factor productivities and factor prices to differ across countries. It reformulates ranking proportions derived from the Heckscher-Ohlin-Vanek equations. Based on these models, it empirically investigates in a cross-industry framework the patterns of international trade for a big sample of countries. The results support the value version of the HOV-model, especially in the case of developing countries. Moreover, the HOV model with perfect competition cannot be rejected in favour of a model allowing for scale economies and product differentiation.