Abstract: A process is described for determining the stability of asphaltenes in oil fields, which comprises the following steps: a) titrations of stock tank oil are carried out; the values measured are then used, together with physico-chemical analyses of the stock tank oil, to thermodynamically characterize the asphaltenes and the heavy oil fraction; b) using the physico-chemical analyses of live oil, the experimental data relating to its phase behavior are interpolated in order to provide a better representation by means of an equation of state; c) using the equation of state thus calibrated and the characterization of the asphaltenes, the stability of the latter is verified in relation to the temperature and pressure of live oil, using the equation describing the behavior of a sterically stabilized colloid.