Abstract In vitro inhibition of Heterobasidion annosum by fungi isolated from the surface and inside of Norway spruce ( Picea abies L.) stumps, ten Verticillium bulbillosum strains from Fagus sylvatica L. mycorrhizoplane, and three lignivorous basidiomycetes from culture collections was evaluated at 5, 10 and 15°C in a search for potential biocontrol candidates. Forty-nine strains from nine genera and hyaline sterile mycelia with or without clamp connections were isolated from spruce. Over 50% inhibition at one or more temperatures was displayed by 21 of 49 isolates. Fresh wood tests were also performed with the six fungi that displayed the highest in vitro activity and with the basidiomycetes. The best results were observed with Hypholoma fasciculare, Trichoderma harzianum 7 AO , Verticillium bulbillosum (culture filtrate) and Phanerochaete velutina.