The dielectric loss (epsilon '') properties of MgB2 composites were investigated by using the conductance-voltage (G/w-V) measurements in the wide frequency and applied bias voltage range at four different temperature levels. Experimental results show that both G/w and epsilon '' are found strong functions of frequency and applied bias voltage for each temperature level. These changes in G/w and epsilon '' are considerably high especially at low frequencies and temperatures. The values of epsilon '' decrease exponentially with increasing frequency until 100 kHz and then become almost constant. Such behavior of G/w and epsilon '' shows that interfacial polarization is more effective especially at low frequencies. In addition, the current-voltage (I-V) characteristics were also evaluated for 100, 200, and 300 K, and the I-V curves for each temperature show linear behavior. Results indicate that the G/w-V measurements may be a useful tool to characterize the dielectric properties and conductivity of MgB2.