Abstract: A brown, slowly growing unidentified fungus was isolated from nine (chlorophyll-free, yellowish-green and green) individuals of Epipactis helleborine (L.) Cranz collected from Finland. The brown fungus appeared regularly from sterilized root segments, and four isolates were obtained from hyphal coils in cortical cells of both green and white individuals. The results indicate that the same endophyte inhabited white and green plants of E. helleborine, and that the brown fungus can be considered to be the endophyte of this species, though this has not yet been confirmed with symbiotic tests. The effect of different surface-sterilizing agents on the appearance of the brown fungus from root pieces was investigated. The most suitable sterilization chemical proved to be 0.1% mercuric chloride in 50% ethanol. The morphology and some characteristics of the fungus are described. The growth pattern and microscopic chracateristics of the brown endophyte differ from those of the well-known orchid fungi. No teleomorph could be obtained in culture.