Oil is undoubtedly rather more than a mere hydrocarbon. It is a development factor, an essential element in energy balances, a strategic weapon, a resource characterized by unequal distribution, and also by unequal consumption. For more than a century now, it has showed its importance, whether during periods of crisis, or at times of strong growth. Under such circumstances, few countries have allowed mere market laws to operate freely. Whether visible or discreet, the hand of the State has been present in many cases, depending on different purposes and taking various forms. Hence national companies developed, if only in order to deal with the Majors and their greatly feared power. One finds examples of national companies both in Western Europe and in certain developing countries that have substantial resources on their soil. Those companies did not all experience the same destiny, but they have sometimes influenced the rules of the oil game. The colloquium held in Paris in 2003 («National oil companies: history, characteristics, comparisons from the inter-war period to the end of the 20th century») provided some new facts and viewpoints in connection with this history, still relatively unknown. You will read contributions here from various horizons making it possible to illuminate the present and the near future, since oil industry issues continue to challenge the world.