Abstract: The distribution of Scots pine mycorrhizal types and the cytopathology of selected mycorrhizae were studied in the surroundings of a fluting mill in Central Finland. A decrease in the mycorrhizal types was observed in the close vicinity of the factory. The mycorrhizae showed several disturbances in their ultrastructure, the most important being accumulation of tannins in the root cortical cells, intracellular penetration by the ectomycorrhizal fungi and accumulation of electron-dense deposits m the fungal vacuoles. The trees with only slight crown injuries showed clear injuries in their rootlets and mycorrhizae. A rapid staining method, Ponceau S, was tested for stammg pme mycorrhizae and the results of some staining trials are reported.