The heat capacities and enthalpy increments of strontium bismuth niobate SrBi2Nb2O9 (SBN) and strontium bismuth tantalate SrBi2Ta2O9 (SBT) were measured by the relaxation method (2-150 K), Calvet-type heat-conduction calorimetry (305-570 K) and drop calorimetry (773-1373 K). The temperature dependences of non-transition heat capacities in the form C-pm = 324.47 + 0.06371T - 5.0755 x 10(6)/T-2 J K-1 mol(-1) (298-1400 K) and C-pm = 320.22 + 0.06451T - 4.7001 X 10(6)/T-2 J K-1 mol(-1) (298-1400 K) were derived for SBN and SBT, respectively, by the least-squares method from the experimental data. Furthermore, the standard molar entropies at 298.15 K S-m(o)(SBN) = 327.15 +/- 0.80 and S-m(o)(SBT) = 339.23 +/- 0.72 J K-1 mol(-1) were evaluated from the low-temperature heat capacity measurements. (c) 2006 Elsevier B.V. All rights reserved.