Ectomycorrhizas of Scots pine (Pinus sylvestris L.) and beech (Fagus sylvatica L.) were sampled in a mature forest ecosystem exposed for more than 40 years to moderate levels of gaseous and dust pollutants. Soil of the forest site was characterised by low pH and accumulation of heavy metals (Pb, Mn, Zn, Cu, Cd, Fe). Mycorrhizal vitality and enzyme activity of the root-surface and soil acid phosphatase (AcPase) were studied at 17 measurement points (0–5 cm soil depth) in relation to the content of inorganic phosphate (Pi) and aluminium ions (Al3+) in the soil. Anatomy of Scots pine and beech mycorrhizas taken from different measurement points was observed. The concentration of essential nutrients (C, N, P, Ca, Mg) and the ratios Ca/Al, Mg/Al and N/P were analysed in fine roots. High concentrations of Al3+ in the soil (40–118 meq kg-1) and low levels of Pi (12–44 mg P2O5 kg-1) were accompanied by high activity of the root-surface AcPase of pine and beech mycorrhizas (25–67 and 33–86 μmol pNP g-1 fresh weight h-1, respectively) and soil AcPase (6.8–22.4 μmol pNP g-1 dry weight h-1). The results indicate that fine tree roots are undoubtedly under stress as evidenced by a disturbance in P uptake and accumulation. However, the high vitality of mycorrhizas and the high Ca/Al ratio in fine roots suggest that the defence mechanisms of mycorrhizas and the rhizosphere are still able to ameliorate the influence of anthropogenic pollution.