The 1 MHz dielectric properties for single-phase polycrystalline ceramics of the Ca5Nb2TiO12 and Ca5Ta2TiO12 perovskites are reported. In the vicinity of ambient temperature, the dielectric constants are approximately 35 and 23, respectively, and the dielectric losses are low, with Qs on the order of 5000, the upper limit of our measurement technique. Ceramics with a temperature coefficient of dielectric constant (TCK) less than 5 ppm/degrees C are reported. The dielectric properties are found to be systematically dependent on processing conditions. The data suggest that an order-disorder transition among the B-site ions plays a major role in the determination of the temperature dependence of the dielectric constant for both compounds.