Cryptosporiopsin, hyalodendrin, and scytalidin, fungal metabolites with antibiotic properties, were tested for fungicidal efficiency using a SoilBlock technique similar to the American Wood-Preservers'Association Standard M10-74, with Lenzites trabea (Pers.)Fr. As test fungus. Cryptosporiopsin was most effective with a threshold value of about 2.3 kg/m₃ (0.14 lb./ft.₃) followed by hyalodendrin with 3.3kg/m₃ (0.20 lb./ft.₃) and Scytalidin with 7.2 kg/m₃ (0.45 lb./ft.₃). The threshold values estimated for the two control compounds were about 2.0 kg/m₃ (0. 13 lb./ft.₃) for the pentachlorophenol mixture (88% pentachlorophenol and 12% 2, 3, 4, 6 -- tetrachlorophenol) and about 15 kg/m₃ (0.94 lb./ft.₃) for sodium arsenate.