Formation process and microwave dielectric properties of the R2V2O7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV2O6 phases, which were formed at 300 degrees similar to 500 degrees C by the reaction of RCO3 and V2O5, interacted with remnant RCO3 to form the homogeneous triclinic R2V2O7 phases at 600 degrees-700 degrees C. The Sr2V2O7 and Ca2V2O7 ceramics sintered at 1000 degrees and 950 degrees C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of epsilon(r)=10.4-12.1, Q x f=15 200-19 520 GHz, and tau(f)=-30.9-34.8 ppm/degrees C. However, the Ba2V2O7 ceramic was well sintered at 900 degrees C for 10 h and it showed the good microwave dielectric properties of epsilon(r)=10.1, Q x f=51 630 GHz, and tau(f)=-26.5 ppm/degrees C.