Dielectric ceramic compositions for microwave applications belonging to the (BaO)-(Nd2O3)-(Sm2O3)-(TiO2) phase diagram were studied. Two compositions were selected for study, the doping effect of MnO2, WO3, CaO on dilatometry, microstructure and microwave properties. The effect of the nature and the amount of dopants on microstructure and microwave properties were clearly demonstrated. The effect of the addition of 1 or 2 wt % WO3, MnO2 and CaO to Ba-4 (Sm-0.6, Nd-0.4)(9.33)Ti18O54 and Ba-3.75 (Sm0.5Nd0.5)(9.5)Ti18O54 was studied. It was found that these two compositions lead to dense ceramics exhibiting excellent microwave properties, for instance epsilon = 74-81, Qx f up to 9000 Ghz at 3 Ghz and tau(f) around + 9 p.p.m. degrees C-1.