Knowledge of the chemical speciation and distribution of chromium at hazardous waste sites is essential for adequate site characterization and risk assessment. Contaminant speciation, whether dissolved or in association with solid surfaces, will affect the toxicity and mobility of most contaminants in subsurface systems. This is particularly true of chromium, which exists as Cr(VI) and Cr(III) species in subsurface systems. The chemical speciation and distribution of chromium on unsaturated contaminated soils, and saturated aquifer sediments was analyzed in the vicinity of a chrome plating operation. Sequential extractions and selective ion exchange experiments were performed to infer mineral fractions responsible for retention of the chromium on the solid phase, and the chemical form (speciation) of the retained chromium. Reduction of Cr(VI) to Cr(III) and subsequent precipitation as (Fe,Cr) (OH)3 is proposed as the primary attenuation mechanism in the unsaturated soils immediately beneath the shop. Chromium reduction in the saturated aquifer sediments is significantly less effective in attenuation of the delineated Cr(VI) ground-water plume. Scanning electron microscopy with energy dispersive X-ray analyses, and cursory modelling efforts with CHROMAT were also used to complement wet chemical methods in assessments of chromium transport and transformation.