SUMMARYA field study was conducted to determine the spatial distribution and temporal persistence of Laccaria bicolor (Maire) Ortori genotypes associated vvuli nafuralh tolotiizcd Norway spruce [Ficea abies (L,) Karst,] in a plantation. Groups of sporophores around three trees were mapped and collected over two to four consecutive autumn seasons to isolate cultures and determine their genetic relatedness by mating t\pe and randomly amplified polymorphic DN.^ (RAPD) analysis. Annual sporophore distribution varied significantly on all sites, with an increase in the mean radial distance from the trees over the study period. Sporophore distribution was discontinuous and characterized by clumped groupings around trees. Sporophores with the same mating type and disparate distributions were present on each of tw o sites during the sample period. RAPD analysis for each of the SIS randotn primers detected ihe same DNA polymorphisms for all dikaryolic isolates tested from a gi\ en site over the sample period. These results provide evidence that a single genetic individual of L. bicolor can remain associated with a host root system for at least 3 yr and vary significantly in its spatial distribution. This is the first instance in which the persistence of specific genotypes ol" an early-stage ectomycorrhizal fungus has been demonstrated for a tree colonized by natural sources of inoculum. The impltcations of these findings are discussed in relation to the ecology and succession of ectomycorrhizal fungi.