Mr. Vukan R. Vuchic deals with the latest developments of metro networks and with their future state in the 21st century. He recalls the basic characteristics of metro and the positive and stimulating role it can play in large cities. While its first networks were opened more than a century ago, metro still knows an important growth: for example, it is the best adapted means of transport in some large cities in developing countries. Furthermore, technical improvements and a diversification of existing systems allow an ideal adaptation to the particular conditions of each city. At the end of the article, the author goes on with the debate begun in the issue 3/1986 of the Revue following the World Bank study.