Section 121 of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (SUPERFUND) calls for hazardous waste site remediations which permanently and significantly reduce the volume, toxicity, or mobility of hazardous substances, pollutants, and contaminants. Traditional engineering technology has concentrated on reduction in volume and mobility as assessed by chemical and geophysical measures. It was assumed that accomplishment of volume and mobility reduction would lead to reductions in toxicity. Environmental scientists long have argued that this assumption might not be the case. However, lack of consensus on how complex hazardous waste mixtures should be measured toxicologically hampered integrated assessments. Therefore, a battery of aquatic and terrestrial bioassays was assembled and evaluated comparatively against several chemicals and waste site chemical mixtures. The bioassays were then applied to a mobility reduction demonstration to assess its overall chemical, physical, and biological performance. Results indicated that, while the primary objective of mobility reduction seemed to be achieved, undesirable secondary effects (toxicity) were introduced. These trade-offs must be considered in the holistic sense when remediation measures are being implemented.