The nuclear behavior, vegetative incompatibility, and induction of basidiocarp formation and basidiospore germination of Inonotus andersonii was investigated. Safranin O-KOH and Hematoxylin stains were used to determine the number of nuclei in basidiospores, vegetative hyphae, and basidiocarp tissue. Both uni- and binucleate basidiospores were found in the tubes of basidiocarp tissue. The nuclei in the hyphal cells of presumptive heterokaryons typically numbered some multiple of two per cell which suggests that division is conjugate. Subhymenial hyphae and immature basidia were often uninucleate but tramal hyphae were multinucleate. Antagonistic hyphal interactions developed between different vegetative isolates on both 2% MEA and oakwood test blocks. Self-crosses were compatible. Basidiocarps formed in 12 wk on 2% MEA medium containing ground oakwood and wheat. Most attempts to induce spore germination failed. However, basidiospores obtained at the end of this study from actively sporulating basidiocarps germinated on 2% MEA.