The article deals with the change of crown defoliation of Scots pine trees (Pinus sylvestris L.) in the Siemianice Experimental Forest Division on the basis of observations conducted in 1996 and 1999. The discussion comprises the distribution of the level of defoliation, share of degrees of opening according to European classification, defoliation indices and means of tree crown defoliations of 1-3 and 4-5 Kraft classes. The crown state of pine trees in the Siemianice Experimental Forest Division improved considerably during three years. This process is more visible in the case of trees of 1-3 Kraft class than in 1-5 Kraft class, which testifies to a greater vitality of trees from the primary stand. Mean defoliation and defoliation indices of trees of the primary stand and of the entire stand are clearly connected with age classes. Changes in the condition of crowns of pine trees recorded in the examined forest division depict favourable processes in pine stands, which have been taking place since 1995.

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