A new bitumen model has been proposed. The model is a more complete mathematical description of the stability of bitumen in terms of three-dimensional solubility parameters. It could easily be visualised in a 3D diagram or a physical model. The model is based on the current knowledge of bitumen chemistry combined with investigations on the solubility parameters of the least soluble components of bitumen. For this purpose we have used turbidimetric titrations with three carefully selected titrants, iso-octane, 2-butanone and 2-ethyl-1-hexanol. The result is a stability space expressed in terms of Hansen solubility parameters. The model indicates that the stability of bitumen depends on the mutual solubility of all components of bitumen, a statement which is contradictory to the "old" ideas of bitumen consisting of a dispersion of asphaltene micelles. We have found that if the chemical environment in the bitumen is changed too much, there is a risk for precipitation of the least soluble component which means that the bitumen becomes unstable. We suggest that this is accompanied by a loss of functional properties of the binder. In this work we have shown that stability changes can go in different directions depending on the kind of process we are considering. Examples are ageing, oxidation, visbreaking, fluxing or blending bitumens. The new model permits us to predict bitumen stability and calculate its sensitivity for different kind of changes. From this, it follows that the model is a good tool for making a more proper choice of blending components. We believe that the new model could provide the base for a new description of bitumen, which could be used to better understand the performance properties.