The Division of New Technology, Materials, and Research (NTM&R) of the California Department of Transportation sought a method to measure the spatial distribution and movement of moisture in a pavement section. Measurement of electrical resistivity was investigated because of the inverse relationship between resistivity and moisture content. NTM&R collaborated with Lawrence Livermore National Laboratory in applying electrical resistance tomography (ERT) to measure and subsequently image spatial resistivity. The results from two field experiments succeeded in showing images that correlate very well with layers in pavement sections. Images from sequential ERT measurements reveal water movement within the pavement and into the subgrade. Results suggest that ERT technology may be an important research tool in understanding moisture distribution and movement.