'Oxalis acetosella', a common plant of 'Pino-Quercetum' forest in Poland, was used to estimate the effect of several kinds of industrial dusts on arbuscular mycorrhizal colonization. The research was done on experimental plots treated in 1980 with cadmium, zinc and aluminium dusts (collected from electrofilters) at levels ranging from 100 to 5000 t km⁻². Mycorrhizal colonization of '0. acetosella' roots was usually higher in the samples collected from the cadmium and zinc dust-treated plots and was accompanied by increased water availability measured as stomatal resistance. Subsequent fertilization of these plots resulted in a decrease of mycorthizal infection but at the same time an increase in photosystem II damage was observed. Neither the use of aluminium dust nor the fertilization following the dust treatment had any significant effect on mycorrhiza formation in '0. acetosella' roots.