Our paper presents results of investigations aimed at determining correlations between the content of polycyclic aromatic hydrocarbons (PAHs) and the enzymatic activity of a forest soil on an extensive area of forest damaged by a large fire 12 years ago. The investigations comprised experimental plots in the cultivations of Scots pine (Pinus sylvestris L.) and grey alder (Alnus incana L.) MOENCH on three sample surfaces on which different methods of soil preparation were applied. The statistical analysis of the obtained results clearly showed the inhibiting influence of the PAH content on the activity of dehydrogenases, acid phosphatase, alkaline phosphatase and protease, which indicated that the examined soils were loaded with PAHs to such a degree that it was dangerous to living organisms. A highly significant positive correlation was found between urease activity and PAH content.