Chlorotic patches in a three year old ley of Lolium perenne L. were associated with high concentrations of cadmium, lead and zinc in the soil. L. perenne in these patches was severely affected by Drechslera leaf spot. When cadmium at 10 to 25 μg cm−3 was added to plants grown in solution culture, or in soil as simulated swards, levels of disease resulting from inoculation were up to 10 times greater than on plants grown in cadmium-free solution or soil. Cadmium reduced the dry weight of roots and especially shoots in both inoculated and uninoculated plants and accumulated in root and shoot tissues. Cadmium uptake decreased the uptake of potassium.