The results of a study carried out in 1989-1990 among the executives of the national French railway company (SNCF), concerning the notion of network, are presented in this article. Here the term network is applied to passenger transportation and to the effects on travel resulting from the introduction and development of high-speed train travel. This analysis brought out the existence of two broad notions for the term network, which are in fact two dimensions of the concept itself. The first is the traditional one, recognized by all those consulted, and relates to infrastructures. "Network" here means links and physical nodes. The second notion is much more recent and was not expressed as such by those questioned: here, "network" introduces the idea of the variety of services provided, their conception and content. The tendancies observed would seem to suggest that a loss in territorial continuity in the support network may be related to a certain continuity made possible by a service network.