The important issue of energy remains central to the development of the world's economy, the competitiveness of nations and manufacturing enterprises, geopolitical equilibrium and the processes that affect this equilibrium. The majority of the globe has suffered reduced economic development and the issue of energy is consequently affected by the growth of the energy industry, its economic performance and the organisational and financial evolution. This paper thus deals with these issues and aims to analyse the economic and financial structure, the strategic directions and the social assets of the 30 major oil companies in the United States on the one hand and that of the Italian Group ENI on the other. The analysis uses official data from 1977 to 2001 and shows that over the last 5 years the energy industry of the United States has used a strategy that focused on its energetic core business, investing in acquisition of petroleum foreign property, although at the same time diversifying its content by entering into the area of electric energy. ENI chose the same strategic model for development, although the Italian operator chose not to carry out large mergers and acquisitions, in this way achieving (proportionally) much higher returns than the American companies.