Book excerpt: Time domain electrometry (TDE) is a general term which includes time domain reflectrometry and time domain transmissiometry. It is a commercially-viable technique for leak detection, contaminant monitoring, and moisture content determination in contaminant transport modelling. Under demographic pressure, contaminated sites are increasingly being re-developed for domestic and industrial use; and this presents an urgent need for reliable, non-intrusive and integrated methods of subsurface characterization, detection and monitoring of organic and inorganic pollutants, soil moisture content and salinity. This book provides an overview of the potential application of TDE in geoenvironmental engineering and describes the geophysical methods used.