The cell free culture media of 16 ectomycorrhizal fungi were tested for their ability to inhibit the growth of 23 phytopathogens and one ectomycorrhizal fungus. Extracellular metabolites of seven (44%) ectomycorrhizal fungi, Amanita citrina, Laccaria bicolor, Laccaria Iaccata, Pisolithus tinctorius, Suillns brevipes, Trircholomo flavovirens and Tricholoma pessundatum, inhibited the growth of up to 20 of 24 (83%) fungi tested. Two ectomycorrhizal fungi, P. tinctorius and T. pessundatum, were inhibitory to the ectomycorrhizal fungus, Sphaerosporella brunnea. A microscopic examination at the colony margin of confronted phytopathogenic fungi was made, noting changes in hyphal morphology. A novel feature, hyphal lysis, caused by the cell free culture medium of P. tinctorius, was seen in the two phytopathogens, Truncatella hartigii and Rhizoctonia praticola, and in the hyphae of the ectomycorrhizal fungus, S. brunnea.