The heat capacities and enthalpy increments of strontium bismuth niobate SrBi 2Nb 2O 9 (SBN) and strontium bismuth tantalate SrBi 2Ta 2O 9 (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 + 0.06371 T − 5.0755 × 10 6/ T 2 J K −1 mol −1 (298–1400 K) and C pm = 320.22 + 0.06451 T − 4.7001 × 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 ° ( SBN ) = 327.15 ± 0.80 and S m ° ( SBT ) = 339.23 ± 0.72   J   K − 1   mo l − 1 were evaluated from the low-temperature heat capacity measurements.