The bark of five healthy and six declining silver firs (Abies alba Mill.) was artficially wounded in July 1991. Structural changes were observed 6, 9, 16,23, and 40 days later. After 6-9 days, there was necrosis and deposition of polyphenols in the exposed tissues. Hypertrophy of the axial and ray parenchyma, and hyperplasia of the rays resulted in the formation of a parenchymatic zone below the necrotic tissues. The outermost cells of this zone just below the necrotic tissues exhibited thickening of walls and lignification in the corners of individual cells. Except in two apparently healthy trees and one strongly declining test tree, intracellular suberin was detectable in some lignified cells by day 16. By then polyphenols were visible in the axial parenchyma cells underneath the parenchymatic zone. Between 23 and 40 days after wounding, progressive suberisation resulted in the formation of a 'ligno-suberised zone', which fused with the phellem of the pre-existing periderm. By day 23, initiation of a new phellogen internal to the 'Iigno-suberised zone' was observed. By the end of the experiment, the necrophylactic periderm did not fuse with the pre-existing periderm. The cells with brown deposits underlying the parenchymatic zone were not noticed on day 40. Suberisation coincided with the imperviousness detected in all trees by day 23. The bark response to mechanical wounding was essentially the same in healthy and declining trees.