Enthalpy, Gibbs energy of formation, absolute entropy and heat capacity of purines and pyrimidines were calculated in the solid state and in dilute aqueous solution from a single reference state. Properties in the solid state were calculated from combustion data. Properties in dilute aqueous solution were calculated from solubility data and pK values after reconciliation. From this complete set of consistent data, the transformed properties were calculated. Missing data were made up using chemical group contribution techniques giving the formation properties of some chemical bonds specific to purines and pyrimidines.