A research project was undertaken to study the effectiveness of soil vapor extraction, a technology for remediation of soils contaminated with volatile organic compounds. As part of the project, two soil vapor extraction systems, Site D and Site G at the Twin Cities Army Ammunition Plant, were selected for evaluation. Site information regarding residual soil concentrations before and after treatment were gathered to compare residual levels of volatile organics before and after treatment. Operational data are analyzed to present the performance of the systems and the progression of treatment with time. Capital as well as operating and maintenance costs are presented. Results of the evaluation indicate that soil vapor extraction has been effective in reducing the residual concentrations, generally by several orders of magnitude. In most cases, residual concentrations were nondetectable. The variability of the concentrations, when detectable, also decreased. Samples taken in silty clays and waste materials showed the highest residual concentrations. Operational data indicated that mass removal rates decreased rapidly during the first few days of treatment, and within a few months reached a level one tenth of the initial rates.