  Measurements of the temperature dependence of the surface resistance at 3 GHz
of 100 micron size grains of MgB_2 separated powder are presented and
discussed. The microwave surface resistance data is compared to experimental
results of Nb, Bi_2Sr_2CaCu_2O_{8+\delta} (BSCCO) and theoretical predictions
of s-wave weak coupling electron-phonon theory (BCS).
