Major urban centres are merging with neighbouring urban centres, forming the five so-called metropolitan regions of Zurich, Berne, Geneva-Lausanne, Basel and Lugano. These metropolitan regions do not confine themselves to cantonal or national boundaries. These data are based on the 2000 Census (see Population development components).

The Geneva-Lausanne region extends, in particular, into the territories at the other side of the French border. The Basel conurbation reaches as far as Alsace and Southern Germany, while Lugano extends into Northern Italy. Hohentengen in Southern Germany is part of the Zurich metropolitan region. The major urban centre of Berne now takes in the urban centres (agglomerations) of Thun, Biel, Freiburg and Lyss.

Zurich is the biggest metropolitan region, which statisticians count as including, in addition to the actual urban centre of Zurich, eleven other urban centres stretching from Schaffhausen to Zug and from Baden-Brugg to Rapperswil-Jona-Rüti. This takes in a total of 221 localities with some 1.7 million inhabitants in all.

Of the urban centres in the narrower sense, Zurich is also the biggest with 1.1 million inhabitants, followed by Basel with 480,000 and Geneva with 470,000 inhabitants. If the territories on the other side of the Swiss border are included, the population of the Basel region amounts to 690,000 and the population of Geneva to 640,000

Definition agglomerations and individual towns

Agglomerations are defined using standard statistical criteria. These criteria include the number of inhabitants and population trends, links between built-up zones, the proportion of gainfully employed people among the resident population, the economic structure and its involvement with the city centre through commuters. Boroughs were allotted to agglomerations on the basis of the results of the 2000 census.

Agglomerations and isolated towns (i.e. boroughs which do not belong to an agglomeration but had at least 10,000 inhabitants at the time of the 2000 census) count as urban areas. Rural areas include all boroughs which neither belong to an agglomeration nor are isolated towns.