A pyroelectric enthalpimetric calorimeter for the H‐O reaction was constructed using Pd and Au electrodes on a 2.5‐cm‐diam, 0.3‐mm‐thick LiTaO3wafer. The counter (or common) electrode was of Au. The detector was placed in a chamber and various gases were admitted at pressures slightly above atmospheric. 100 ppm H2in N2was used as the hydrogen source and pure O2as the oxygen source. A thermal signature was obtained on the Pd electrode that was confirmed by a thermocouple attached to the pyroelectric calorimeter. A delayed thermal signature was observed on the Au electrode resulting from thermal diffusion in the LiTaO3substrate of the heat generated at the Pd electrode. The results on the H‐O reaction are in general agreement with the literature on Pd metal oxide semiconductor (MOS) structures. The results demonstrate the utility of the pyroelectric calorimeter.