Remediation of arsenic-contaminated soils by traditional offsite methods is cost-prohibitive and destructive to the ecological system. Effective in-situ stabilization techniques are gradually becoming the methods of choice in reducing the risk of human exposure to arsenic-contaminated soils. The reported study explores potential of water treatment residuals (WTRs) as an in-situ arsenic stabilization strategy. WTRs are the end products at municipal water treatment facilities, generally composed of Fe, Al, or Ca. WTRs typically possess an amorphous structure and have high positive charge. It is anticipated that arsenic oxyanions will be strongly adsorbed by WTR-amended soils, resulting in a lowering of its bioavailable concentration. A laboratory incubation study is in progress to determine the role of WTR-amendment in reducing arsenic bioavalability in two arsenical pesticide-contaminated soils. Two sandy Spodosols from Florida (one with high and the other with low arsenic retention capacity) were contaminated with 450 mg/kg of arsenic in the form of sodium arsenate. Following 4 mo of soil-pesticide equilibration, Al-, Ca- and Fe-WTRs were applied to the arsenic-contaminated soils at four rates (0, 2.5, 5.0 and10% WTR by weight). The soils are being periodically (0-time, 6 mo, 1y) subjected to an in-vitro bioavailability method to determine potential arsenic concentrations in the simulated human gastrointestinal system. The 0-time and 6 mo data gathered so far suggest that the WTRs are capable of reducing the bioavailability of soil arsenic. The composition of the WTRs and the varying amendment rates appear to influence the amount of arsenic that is stabilized in the soil. The Al-WTRs are most effective in decreasing arsenic bioavailability, followed by the Fe-WTRs; Ca WTRs appear to have the minimal effect on bioavailable arsenic concentrations. If successful, this remedial option could be further developed into a cost-effective technique to reduce health risk from exposure to arsenic in contaminated soils.