Differential scanning calorimetry was used to study the water of hydration of all of the nucleosides at 59% relative humidity. Hydration was observed in pristine samples of guanosine, (rG), deoxyguanosine, (dG), and deoxyadenosine, (dA). Two inequivalent water sites were observed in dG and one site in rG. Re-hydration was observed in rG and dG, but not in dA. The activation energies for rG were 0.697 ± 0.051 eV and 0.683 ± 0.090 eV for pristine and cycled samples respectively. dG had activation energies of 0.726 &plusmn 0.026 eV and 0.997 ± 0.034 eV for the first and second peaks in the pristine samples while the activation energy for cycled dG was 0.671 ± 0.133 eV.