Morphometrical comparison of nine strains of lithobionic black yeasts Phaeococcomyces exophialae was carried out. Morphological parameters of the following stages: chlamydosphores, yeasts, mycelium and pseudomycellium were measured using the morphological index (MI) and investigated strains were grouped in correlation clusters. It was shown that the population under investigation is moderately heterogeneous but have some morphological groups inside. It could be a result of stressority of their natural habitat (marble) which usually leads to high variability.