A fundamental question in continental deformation studies is whether the surface deformation is accommodated in a distributed fashion or on the edges of a series of rigid blocks. We are addressing this question for the Aegean and western Turkey. We have determined a model strain rate field from an inversion and interpolation of almost 300 GPS velocities from six different studies. In the process of obtaining a best fit between a model velocity field and the GPS velocities, no a priori assumptions about plate rigidity have been made. On the other hand, we have placed constraints on the distribution and style of zones of weakness within the region. These zones of weakness and their inferred style correspond to our knowledge of active faults in the region. We find that regional shear strain rates are extremely localised along the North Anatolian Fault ? North Aegean Trough (NAT) system and that extensional strain rates are significant mainly along the Corinth Gulf. Low levels of extension are found in parts of central Greece and western Turkey as well. Most of the southern Aegean Sea and Peloponnesus appear to be relatively rigid (i.e., Aegean block). A rigid Anatolia and ?South-Marmara? block (the latter extending from Sporades in the west to close to the city of Bursa in the east) can also be distinguished. We thus conclude, like some others have before, that the vast majority of the regional kinematics can be understood by considering a set of rigid blocks, with only northern Greece, parts of western Turkey, and the region between the South Marmara and Aegean blocks acting as zones of diffuse deformation. We attempt to correct the inter-seismic GPS velocities for elastic loading effects by modelling the most active faults with an elastic-half space model. The resulting GPS velocity field, which is thought to be a closer representation of the long-term velocity field, confirms our findings and allows us to estimate relative Euler poles for all proposed blocks. We test the appropriateness of our block-model by comparing predicted motions with observed velocities.