The basicity of the neutral form of a series of dipeptides having valine as common first term has been studied from the calorimetric and statistical points of view. This was achieved by using the proton transfer processes of these compounds in the aqueous and the gaseous phase. The values of the thermodynamic quantities for these proton transfer processes (with valylvaline as reference compound) vary as a function of the structure of the second component, so that two relative scales of basicity, in the aqueous and in the gaseous phase, are found. A relationship which compares the proton dissociation processes of the free amino groups of the dipeptides with that of the corresponding free first alpha-amino acid (the first component) supplies, on an absolute scale, the percentage values of the basicity variation in the dipeptides. Finally, a monoparametric linear regression analysis leads (in terms of probability) to the hypothesis that the structure of the second component influences in a different way the proton transfer processes (and thus the basicities) of the dipeptides in aqueous and gaseous phases.