Up to 1860 Geneva was the natural urban center towards which the rural areas of the French Pays de Gex and of Haute Savoye tended, and until 1914 the frontier between the Canton of Geneva remained perfectly open; but whereas there were no difficulties to exchanges, there were some reasons why Genevan capitals were not invested in the French territory. It was World War I, however, which determined the closure of the borders, and the ensuing disintegration of the Genevan regional structure. Geneva re-oriented itself towards the interior of Switzerland and towards the inter-national context, while Haute Savoye started its own process of industrial growth. Nowadays the amazing rate of urban-industrial growth of Geneva, which passed from 202,918 to 331,599 people between 1950 and 1970, involves difficult problems in the relationships with the French hinterland. The author considers in some detail only two of them; the problem of ''frontalières", the cross-border commuters, who have grown from 2,349 in 1960 to more than 20,000 in 1972; and the problem of the purchase of French land by Genevan citizens, for agricultural but especially for secondary housing pur poses. Such phenomena involve no mean problems of economic and taxing standardizations, of social justice, of urban and industrial planning; it is suggested that the best possible solution is to give the Franco-Genevan border an updated version of the earlier permeability.