[en] Soil decontamination of soil contaminated by low-level activities of radionuclides, mainly by caesium-137, which come from accidental releases by maintenance of nuclear devices and by liquid wastes reprocessing, is long-term and expensive technology. Knowledge of the causations, which control the processes of bioaccumulation of radionuclides, is a necessary condition for critical assessment and successful utilization of processes of bioremediation in situ in practise. The authors present the experimentally gained quantitative values of bioaccumulation of caesium-137 from water solutions by micro organism cultures of Rhodotorula aurantiaca CCY 20-9-1, Sacharomyces cerevisiae, Rhodococcus rhodochrous ATCC 15906, Streptomyces sp. DX-IX, Coriolus versicolor CCWDF-14 and Rhizopus sp. R-18. Intensively growing cultures reach the highest values of bioaccumulation; the cultures in non-growing phase reach several orders lower values. From researched micro organisms the highest values of bioaccumulation of Cs⁺ 5.1 pmol/g (wet weight) at initial concentration of Cs⁺ in solution co = 1 nmol/l (without carrier) and 29.2 μmol/g (wet weight) at co = 6 mmol/l Cs⁺ (adding of carrier CsCl) were found out at growing culture S. cerevisiae as model of eukaryotic cell after an achievement of maximal stationary grow phase. Acquired information refer to the possible role of soil micro organisms at bioaccumulation of ¹³⁷Cs in contaminated soils and their potential utilization in lowering of radioactive contamination of environment (authors)