Saturation molalities m(sat) in H2O(l) have been measured for the substances adenosine(cr), guano sine (.) 2H(2)O(cr), inosine(cr), and xanthosine (.) 2H(2)O(cr) over the temperature range T = 287.91 K to T = 308.18 K by using h.p.l.c. The indicated states of hydration of these substances were established by performing Karl-Fischer analyses of samples of these substances which had been equilibrated over H2O(l) and of samples obtained by passing air over the wet crystals (air dried samples). The crystalline phases of these substances were identified by comparison of the results of X-ray diffraction measurements with results from the literature. Molar enthalpies of solution Delta(sol)H(m) for adenosine(er) and inosine(cr) were measured by using an isoperibol solution calorimeter. A "stacking" or "self-association" model was used to estimate values of the activity coefficients gamma and relative apparent molar enthalpies L-phi for these substances. These gamma and L-phi values were used to adjust the measured values of m(sat) and Delta(sol)H(m) to the standard state and obtain values of the standard molar Gibbs free energy and enthalpy changes DeltasolG(m)degrees. and Delta(sol)H(m)degrees, respectively, for the dissolution reactions of these substances. Values of Delta(sol)H(m)degrees calculated from the temperature dependence of values of Delta(sol)G(m)degrees were in good agreement with the values of Delta(sol)H(m)degrees obtained by using calorimetry. Published by Elsevier Ltd.