Cement kiln by-pass dusts from Canada Cement Lafarge Ltd. plants at Woodstock and Bath, Ontario, respectively, were tested as limestone substitutes in reclaiming acid, metal-contaminated soils from the Sudbury area. Laboratory, growth chamber and field trials showed that both dusts constituted effective liming materials at an application rate of approximately 10 t/ha . Toxic effects were found only in the case of Bath dust, at an application rate of 50 t/ha. In sandy soil, Bath dust at 50 t/ha also inhibited seed germination. This inhibition disappeared after a few days, presumably due to the leaching of soluble alkaline materials and chlorides. In pots, the addition of N-P-K fertilizer lessened the toxic effect of Bath dust, while in the field it converted the effect of the dust from inhibition to stimulation. These by-pass dusts have good potential as liming materials in reclaiming Sudbury's industrial barrens, but their caustic nature precludes their use at this time, in view of the predominantly manual application techniques that prevail .