Measurements of the latent heat of transition of ceramic samples of KTaxNb(1-x)O3 from the tetragonal to the cubic phase are reported for values of the parameter x ranging from 0 to 0.18. The latent heat is observed to decrease rapidly as x is increased from zero. The method of sample preparation, apparatus and experimental procedures are described briefly. on the basis of certain simplifying assumptions, the spontaneous polarization at the ferroelectric Curie point is calculated, using the phenomenological theory proposed by Devonshire. © 1959, American Chemical Society. All rights reserved.