Between 1975 and 1999, the Greater Paris area gained more than 500,000 jobs, yet the region's economic geography saw a transformation of its most dynamic locations and industries. If employment has increased in the outer suburbs, the core (centre and inner suburbs), is losing jobs as a result of the large fall in employment in Paris. The movement of jobs away from the centre is the significant phenomenon of the period. It has, for the one half, contributed to the appearance or reinforcement of industrial clusters in peripheral locations and, for the other half, resulted in the extension of the suburban area between and around these clusters. Overall, employment is less concentrated in 1999 than it was in 1975. At the same time, the spatial sectoral concentration has little changed, or even increased. Each industry would become concentrated in a specific part of the region, which would explain both the sectoral concentration and the overall decentralisation. The deconcentration of employment, or spatial disintegration, therefore would occur according to the sector, i.e. vertical disintegration. Logically, this reorganization should lead to the emergence of specialised clusters throughout the region. Also at the same time, however, the structure of employment in these clusters has diversified. The growth of new industries can only explain this in part, the complement being in the local dynamics. The transfer of establishments contributes thus to this regional reorganization. Sent out from the central zones, they essentially benefit at the periphery. Yet these transfers feed local specialisations and do not explain the diversification observed. There exists a clear paradox between an apparent local diversification and the logic of vertical spatial disintegration, which leads more to the specialisation of centres of employment.