The consideration and use of in-situ reactive wall groundwater treatment systems on remediation projects continues to gain acceptance. Such systems are attractive due to their low initial capital costs and their minimal operation and maintenance costs compared to traditional pump and treat systems. These systems often are used as a polishing step to groundwater treatment in conjunction with source removal and natural attenuation. In constructing reactive wall groundwater treatment systems, various specialty construction techniques have been utilized. These techniques have included: deep soil mixing, bio-polymer trenching and slurry walls to successfully build funnel and gate systems with replaceable treatment cartridges as well as permeable treatment walls containing iron fillings. Such systems have been installed in full-scale and pilot scale applications for various private companies, the Department of Energy and the United States Air Force and others. Several case histories are presented to illustrate these various installation techniques and their applications.