Technical Abstract: Cadmium is a heavy metal that occurs naturally as a trace metal throughout the environment. Cadmium is also a potentially toxic metal with no known requirement by living organisms. Various activities of humans have caused the contamination of some soils with cadmium. There is a need to understand the solubility of cadmium in contaminated and uncontaminated soils. This study reports the forms of cadmium found in solution in 64 soils collected in the USA and Canada from fields which ranged from 0.1 to 38 ppm Cd. Soluble Cd varied from 0.03 to 182 ppb Cd. Electrochemically labile Cd was the dominant form in solution, and free uncomplexed Cd comprised about 20% of the total. Solution pH was the main factor controlling cadmium solubility, and ranged from pH 3.5 to 8.1 in this set of disparate soils. The total level of cadmium in the soil contributed significantly to Cd solubility. Neither soluble nor total organic matter had much effect on soluble cadmium, so the levels of cadmium in the soil solution of these soils could be predicted from a relatively simple model based on only pH and total content of cadmium in the soil.