The enthalpy increments of CaZrO3(s) and SrZrO3(s) have been measured by drop calorimetry from 475.6 to 845.6 K, and from 474.4 to 906.5 K, respectively. Some additional enthalpy increment measurements on BaZrO3(s) have been performed from 804.3 to 899.30 K. The results are compared with other measurements on CaZrO3(s), SrZrO3(s) and BaZrO3(s), and these are discussed critically. The heat capacity functions up to 2000 K for the three zirconates are presented.