A new ultra low loss microwave dielectric ceramic, Mg(Sn0.05Ti0.95)O-3 (MSnT), was found and investigated. The compounds were prepared by the conventional solid-state route, and sintered at 1360 degrees-1480 degrees C for 2-6 h. The investigations show that the MgTi2O5 secondary phase was observed. Moreover, the dielectric properties were correlated with the formation second phase. The excellent microwave dielectric properties of Q x f = 322 000 (GHz), epsilon(r) = 17.4, and tau(f) = -54 ppm/degrees C were obtained from the new MSnT ceramics sintered at 1390 degrees C for 4 h.