Cadmium is a heavy metal contaminating soils and sediments threatening human health globally. Generally, Cd is a highly toxic metal and typically bioavailable within soils owing to its weak partitioning within the solids of aerated environments. Despite its weak partitioning to most soil minerals, Cd does tend to bind appreciably to organic matter, sulfide minerals, sulfides and phosphate. The bioavailability of heavy metals in soils is determined by a combination of soil physiochemical factors and physiological traits of the target organism. While elements within the aqueous phase may be readily accessible to plants and animals, binding to soil solids may be one of the significant factors limiting biological uptake. The stability of the solids and the strength of metal retention on or within soils can therefore greatly impact the bioaccessibility of metals such as cadmium. Here we evaluate the bioaccessibility of cadmium within soils from throughout the U.S., including current and former Department of Defense sites. Additionally, perturbations in biogeochemical conditions induced by soil amendments and ensuing changes in the bioaccessibility of Cd were investigated.