The species composition of microscopic fungi (micromycetes) on the foliage surface of wood and shrub plants in the center and suburbs of Saint-Petersburg was studied. Thirty species of fungi and the sterile forms of light and dark mycelium were detected. Different micromycetes permanently inhabit plant foliage and form communities having characteristic structures. The basis of these communities is constituted by dark colored anamorphic microscopic fungi referred to a few species. They form hyphae and microcolonies, the distribution of which may be related to the structural features of foliage. Micromycetes of phylloplane fungi show antagonistic relationships with powdery mildew pathogens, which also develop on foliage surfaces. The composition of phylloplane mycobiota depends on the spatial arrangement of plantations as well as on their composition. Phyllophilic biofilms associated with dust particles of various shapes and sizes form organomineral layers on foliage surfaces. As a result, fungi are involved in the formation of bioinert systems and in crystallization and mineral formation. In general, the specific features of phylloplane mycobiota development are largely determined by ecological situations in specific areas.