We cloned an intact copy of a long terminal repeat retroelement designated marY1 from the ectomycorrhizal basidiomycete Tricholoma matsutake. The reverse transcriptase domain is found in T. matsutake and Tricholoma magnivelare worldwide. This finding suggests that retroelements associate with ectomycorrhizal basidiomycetes and may be useful as genetic markers for identification, phylogenetic analysis, and mutagenesis of this fungal group.