Heavy metals Zn and Cu in high concentration (2 mM for Zn and 0.5 mM for Cu) have some inhibiting effect on growth of microscopic fungi Aspergillus niger and Penicillium citrinum. Toxic effects of these metals considerably depend on cultivation conditions including nitrogen sources, pH of nutrient media and its consistency (presence or absence of agar). In general nitrate media provides less inhibiting effect on fungal growth under heavy metals exposure than ammonium-containing media. Adding of Zn in nitrate media induces oxalic acid production by fungi. Importance of oxalic acid production in detoxification of heavy metals is confirmed by forming of Zn-containing crystals in fungal cultures. Cu bringing to the cultural media had not stimulating effect on oxalic acid production as well as no copper-containing crystals were observed. But proceeding from essential increase in oxalic acid production during a long-term fungi adaptation to Cu it may be proposed that oxalic acid plays some functional role in Cu-to