Field experience has shown that soil conditions can have large effects on Ground Penetrating Radar (GPR) detection of buried targets of interest. The relative permittivity of the soil determines the attenuation of the radar signal. The contrast between the relative permittivity of the soil and the target is critical in determining the strength of the reflection from the target. In this paper, a microstrip ring resonator is used to measure the relative permittivity of the soil and various target fill materials. For this measurement technique, a microstrip ring resonator is placed in contact with a material medium and the real and imaginary parts of the relative permittivity are determined from changes in resonant frequencies (between 600 MHz and 2 GHz) and the quality factor of the resonator, respectively. Measurement results are compared to data collected by a GPR.