In situ chemical oxidation (ISCO) using permanganate is a technology for treatment of organic hazardous wastes. This research is a review of 30 permanganate (MnO4-) ISCO sites to determine whether there are long term impacts on groundwater quality due to the introduction of the oxidant into the subsurface. A second objective is to determine if manganese concentration can be predicted by trends in specific pre and postoxidation monitored parameters (i.e., pH and oxidation reduction potential (ORP)). The final objective is to identify the effects of site and design conditions on groundwater conditions postoxidation. Results indicate that (1) there are limited long term groundwater impacts due to oxidant introduction (i.e., water quality indicators begin to approach preoxidation levels by 2 years postoxidation), (2) manganese concentrations can be predicted and (3) site and design conditions have pronounced short term impacts on geochemical parameters (i.e., especially site media type, mass of oxidant injected, and initial ORP).