The dielectric properties of bulk polycrystalline ceramics in the binary Ca2Ta2O7-Ca2Nb2O7 system are reported. Measurements of the dielectric constant at 1 MHz were made at temperatures between 0 and 100 degrees C. The large negative (for the niobate) and positive (for the tantalate) temperature coefficients for the dielectric constants in the pure materials in the vicinity of room temperature can be balanced in a two-phase region near x = 0.36 in Ca2Ta2-xNbxO7. At this composition, the dielectric constant is approximately 30, and the temperature coefficient of the dielectric constant is approximately 2 ppm/degrees C. The Q in our unoptimized polycrystalline ceramic at 1 MHz is approximately 5000.