Intra-granular microstructure and stress of tungsten rf magnetron sputtered thin films have been correlated for deposits with stresses ranging from 1000 MPa to −1000 MPa and belonging to the zone T of the Thornton's microstructural diagram. For pure α-W films, the stress values determined from the substrate deflection method were shown to be comparable with those determined by the x-ray diffraction sin2ψ method using the α-W (321) reflection. The lattice parameter a0 of the unstressed material as deduced and was found to depend on the deposition conditions. In addition, a significant broadening of the (321) diffraction peak was observed foi compressive films, which suggests that the intra-granular microstructure has been changed. These original results are interpreted in terms of structural defects: in particular, compressive stress can be related to an interstitial feature.