Publisher Summary This chapter studies the genus Mastigobasidium. In asexual reproduction cells are ovoid or elongate and reproduce by budding and ballistoconidia. Pseudohyphae and true hyphae occur. Clamp connections are absent. Colonies are smooth or delicately wrinkled and whitish, cream, or yellowish-gray. In sexual reproduction it is seen that true mycelium with clamp connections and teliospores occur after conjugation of a compatible pair of mating strains. After a resting period, the teliospores germinate to produce several long hyphae, and clavate, usually curved phragmometabasidia develop on the apices of these hyphae. Basidiospores, which form laterally or terminally, are ellipsoid to bacilliform and are either sessile or arise on pegs. Basidiospores occur singly or in clusters and germinate by budding. In physiology and biochemistry it is seen that fermentation is absent. D-Glucuronate is assimilated. Nitrate is not assimilated. The major coenzyme Q has nine isoprene units in the side chain. Xylose is absent in extracellular polysaccharides. Urease and diazonium blue B reactions are positive. The type species mentioned and accepted is Mastigobasidium intermedium Golubev.