A comparison between healthy and damaged trees growing on the same site confirms that epicuticular wax erosion and stomatal damage are good monitoring markers even in a deciduous broad-leaved with a smooth and compact surface wax layer such as Fagus sylvatica L. As compared to healthy trees, the leaves of damaged ones had a greater quantity of epicuticular wax in June and less in September, an element which indicates the existence of an erosion process. Since the leaves of damaged trees had a higher specific weight, the best erosion indicator in beech trees was found to be the ratio of epicuticular wax weight to leaf dry weight. The processes of erosion and epicuticular layer fusion contributed to damaging the stomata. The most severe stomatal damages observed were: collapse and depression of the guard cells, occlusion by fused wax or wax lumps, fusion or dismantling of the guard cells. Relationship between stomatal conductance and stomatal damage was not observed. In any case stomatal conductance proved of no use for any form of extensive monitoring survey since it is so dependent on meteorological conditions.