In the Master Thesis, we studied the ability of microorganisms to grow at elevated concentrations of hexavalent chromium (Cr(VI)) and the possibility of its reduction to far less toxic forms of trivalent chromium (Cr(III)). In order to verify the hypothesis that the reduction of Cr(VI) with living microorganisms in the sample is more effective than those with the organic matter in the sterile sample, microorganisms in samples from the wastewater collected from the tanerry waste landfill, were isolated and enriched, to be capable of growth at a concentration of 600 mg/L Cr(VI). We tested which concentrations of Cr(VI) inhibited the growth of microorganisms and examined the ability of bacteria to reduce different amounts of Cr(VI) at 24 and 48 hours. Cr(VI) concentration in samples was determined by the spectrophotometry and liquid chromatography in hyphenated to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The results of present investigation confirmed the hypothesis that the reduction of Cr(VI) with microorganisms is significantly more effective than with the organic matter. After 48 hours of incubation, the organic matter reduces negligible amounts of Cr(VI), only at low Cr(VI) concentrations in the medium (5 mg/L). The enriched microbial association almost completely reduced the large amounts of Cr(VI) (5 and 25 mg/L) and more than 50 % Cr(VI) at concentrations up to 100 mg/L in 48 hours. Such high Cr(VI) concentrations may occur in the environment only in the event of ecological disasters or spills. The enriched microbial associations could be applied for remediation of highly polluted wastewaters with Cr(VI).