The dielectric constant and loss tangent of single crystals of BaTiO3were measured as a function of temperature in the frequency range of 8.2 to 12.4 kMc. The technique consisted of looking for transmission resonances through the crystal whenever its thickness became &lgr;/2 (where &lgr; is the wavelength in the material). From the Curie‐Weiss behavior of the dielectric constant in the paraelectric region, theAconstant was determined to be 3.77×10−5°C−1.