Eleven mill tailing samples from locations throughout the Rocky Mountain region were tested for their effectiveness in removal of dissolved contaminants from mine drainage. The average capacity of the tailings tested was 9.8 mg of iron per gram of tailing with a range of capacities from 6 mg/g to 15 mg/g. From these studies it was concluded that for almost all tailing samples, removal was accomplished mainly due to hydrolytic adsorption of metal ions with a small contribution due to the inherent basicity of the tailing. In the other case, removal occurred via reaction with calcareous components of the sample. Continuous column, or stationary bed tests, in the laboratory and in the field were not nearly as effective. It appears that for effective removal a stirred tank reactor will be required.