The A75 motorway bypass of Millau in Aveyron, in south France, requires the construction of an impressive viaduct to cross the Tarn valley. The bridge which will be the highest in the world with piers reaching 240 m in height, will have a steel box section deck with an orthotropic upper flange. The launching will be carried out on steel lattice towers. Steel shows here its exceptional capacities to respond to the challenge of building one of the largest multiple cable-stayed span in a difficult site, at the eve of this new century.