The aim of doctoral work was to evaluate the effectiveness of stabilization i.e. imobilization of potentially toxic metals (PTMs; Pb, Zn, Cu and Cd) by adding hydroxyapatite (HA) and commercial stabilizant Slovakite to soil contaminated with PTMs. The impact of biotic environmental factors (two earthworms species L. terrestris and D. veneta, as a model species) on the fate of imobilised PTMs in remediated soil was also considered. By means of different extraction tests it was determined that both aditives (5 % w/w each) were successful in lowering PTMs bioaccessibility and mobility (extraction tests with dietylenetriaminepentaacetic acid and ethylenediaminetetraacetic acid), phytoaccessibility (extractions with 0,01 M CaCl2 and NH4OAc) as well as in converting the most labile PTMs chemical forms into less labile soil fractions (sequential extraction). Oral bioaccessibility of PTMs was effectively reduced by the addition of 5 % hydroxyapatite (in gastrointestinal fraction concentration of Pb was reduced from 4 to 14 times after remediation), which was determined by UBM (Unified BARGE Method). At the same time functionality and quality of soil were improved due to soil stabilization; activity of Ž- glucosidase and dehydrogenase (DHA) as well as glucose-induced respiration (increased even 5,2 times after remediation) were most sensitive parameters to pH, CEC and PTM potential bioaccessibility changes in the soil, demonstrating their potential as indicators of soil quality. General increase of PTMs bioaccessibility was noticed after earthwormʼs incubation, indicating that the stabilization effect may decrease over time. On the other hand soil functioning after remediation was improved due to earthwormʼs activity. It was reflected in the increased induced respiration rate and increased DHA activity. We also tried to improve soil stabilization by adding tri-sodium salt of [S,S]- ethylenediaminedisuccinate and molasses after soil mixing with hydroxyapatite.