The enthalpies of solution of the hydrated lithium berates Li2B4O7. 3H(2)O and LiB5O8. 5H(2)O in approximately 1 mol . dm(-3) aqueous hydrochloric acid, as well as the enthalpies of solution of H3BO3 in HCl(aq) and of LiCl . H2O in aqueous (hydrochloric acid + boric acid) were determined. With the incorporation of the standard molar enthalpies of formation Delta(f)H(m)(o) of LiCl . H2O(s), H3BO3(s), and H2O(l), the standard molar enthalpies of formation of these hydrated berates were obtained. An approach to correlate Delta(f)H(m)(o) of hydrated berates with Delta(f)H(m)(o) of corresponding cations in aqueous solution and Delta(f)H(m)(o)(H2O, l) was suggested from the point of view of structures,