The enthalpies of solution in water of L-alpha-histidine and its zinc complexes Zn(His)SO4H2O, Zn(His)X-2.1/2H(2)O (X=NO3-, OAc-, Cl-) have been measured at 298.15 K. The standard enthalpies of formation of His(aq) and Zn(His)(2+)(aq) have been calculated. The reliability of the experiment has been discussed.