Activities of extracellular enzymes were determined in beech (Fagus sylvatica L.) leaf litter colonized by the litter decomposer Lepista nuda (Bull.: Fr.) Cooke or by vegetative mycelium from the mycorrhizal fungi Thelephora terrestris Ehrh.: Fr. or Suillus bovinus (L.: Fr.) O. Kuntze. Organic matter (OM) was buried for up to 6 months in plant containers in which mycorrhizal or non-mycorrhizal Pinus sylvestris L. seedlings were cultivated at a low rate of nutrient addition. After different periods of colonization the activities of phosphomonoesterase and protease, two enzymes involved in nitrogen and phosphorus mobilization, were determined in colonized and uncolonized litter. The activities of cellulase, beta-xylosidase, beta-glucosidase and polyphenol oxidase were investigated as indicators of the decomposition capacity of the fungi in the litter. Low activities of all enzymes tested were found in the uncolonized beech leaves. Phosphomonoesterase activity was high in litter colonized with L. nuda or S. bovinus, and was intermediate in the T. terrestris treatment. For all other enzymes the activities in the OM inoculated with the white-rot litter decomposer were considerably larger than those detected in litter colonized by ectomycorrhizal basidiomycetes. Cellulase activity was low in the control as well as in the mycorrhizal treatments. beta-Xylosidase and beta-glucosidase were detected in the litter with mycorrhizal mycelium, whereas polyphenol oxidase activity was only clearly increased in the S. bovinus treatment. These results demonstrate the low lignocellulase activity of both mycorrhizal fungi. This feature reduces the capacity of the mycorrhizal fungi to exploit fresh beech leaf litter, whose endogenous nitrogen is associated with or shielded by refractory compounds. The results are discussed in relation to the role of ectomycorrhizal fungi in nutrient cycling processes in temperate forest ecosystems.