Bitumen is widely used in construction. Its applications go from binder for road asphalts to built-up roofing membranes and other waterproofing uses. The use of crumb tire rubber as a binder modifier may contribute to solving a waste disposal problem and to improving the quality of road pavements. This paper deals with the effect that rubber concentration exerts on the thermorheological properties of rubber-modified bitumens. The results obtained confirm that the rheology and storage stability of these modified binders are largely dependent on rubber concentration. The linear viscoelastic measurements carried out revealed an improvement of both low and high in-service properties of the binder. The viscous flow measurements Showed an important increase in viscosity and a noticeable reduction in temperature susceptibility, A swelling process of the crumb rubber by light components of the maltenic fraction was confirmed by modulated differential scanning calorimetry (MDSC). The stability tests, performed on samples stored at 180 degrees C, demonstrated that the storage stability of rubber-modified bitumen was improved as rubber concentration increased.