The majority of microbes living on forest trees are still unnamed and our knowledge of their species richness is vague. This paper describes the fungal diversity of the above ground parts of a 61 year old Norway spruce tree lacking visible signs of damage or disease. The problem involved with identification of the fungi to named species was circumvented by classifying them into operational chemotaxonomic units (OCTUs) by using their combined fatty acid and sterol profiles (FAST-profiles). The variation of these units was chosen to correspond to a within-species-variation determined for several morphologically defined taxonomic species occurring on Norway spruce. Ninety-nine OCTUs were identified from 666 fungal isolates obtained. Bacteria were found only occasionally from the inner bark samples (three isolates) and from needles (five isolates). Models describing the accumulation of OCTUs against the number of samples taken were used for extrapolation of the total number of fungal OCTUs in the above ground parts of the tree. Our results suggest that an undamaged, apparently healthy Norway spruce, harbours in its above ground parts nearly two hundred fungal species. The majority were estimated to be needle epiphytes. At the large forest area scale, the species richness may be one order of magnitude higher.