We studied the guaiacol peroxidase activity, isoenzyme pattern and metal content in the needles of 2-year-old spruce grown on soils supplemented with cadmium concentrations from 1 to 21 mg kg(-1). Following exposure to cadmium, an initial increase and subsequent decrease in the activity of the soluble fraction was observed. A parallel change of their isoenzyme pattern occurred. An increase of the cell wall-bound peroxidase activity under prolonged metal treatment was evident. The results obtained show that peroxidase activity and isoenzyme pattern could be used to evaluate the capacity of one part of the defense system in spruce seedlings to withstand metal stress.