The production of even a limited number of heterokaryotic spores would be advantageous for establishing new individuals after long distance dispersal. While Suillus and Laccaria species are known to produce binucleate, heterokaryotic spores, this condition is poorly studied for most ectomycorrhizal fungi. To begin addressing this matter the number of nuclei in basidiospores was recorded from 142 sporocarps in 63 species and 20 genera of ectomycorrhizal (EM) fungi. The mean proportion of binucleate basidiospores produced by sporocarps within a species ranged from 0.00 to 1.00, with most genera within a family showing similar patterns. Basidiospores from fungi in Amanita, Cortinariaceae and Laccaria were primarily binucleate but were likely still homokaryotic. Basidiospores from fungi in Boletaceae, Cantharellus, Rhizopogonaceae, Russulaceae, Thelephorales and Tricholoma were primarily uninucleate, but binucleate basidiospores were observed in many genera and in high levels in Boletus. Further research is needed to relate basidiospore nuclear number to reproductive potential in ectomycorrhizal species.