This review presents current views on the features of сhromium and its compounds, their interconversion, reduction of Cr (VI) by microorganisms, as well as the impact of chromium (VI) on the environment and humans. Chromium can have positive and negative effects on health, according to the dose, exposure time, and oxidation state. The most common forms of this metal in biological systems are trivalent Cr(III) and hexavalent Cr(VI). Hexavalent chromium is mobile, highly toxic to humans, and animals and considered a priority environmental pollutant. He is highly soluble and mobile. On the contrary, Cr(III) has relatively low toxicity and mobility and it is one of the micronutrients needed by humans. Сhromium (III) is an essential nutrient required to promote the action of insulin in body tissues so that the body can use sugars, proteins, and fats. Considerable attention is paid to the issues of interconversion of chromium compounds, reduction of Cr (VI) to Cr (III) by microorganisms, as well as physiological features of their action in humans. The present review discusses on the types of chromate reductases found in different bacteria, their mode of action, and potential applications in the bioremediation of hexavalent chromium. Іn the human body chromium (VI) is rapidly reduced to chromium (III) after penetration of biological membranes and in the gastric environment. The reduction of Cr(VI) to Cr(III) results in the formation of reactive intermediates that together with stress oxidative tissue damage and a cascade of cellular events, contribute to the cytotoxicity, genotoxicity, and carcinogenicity of Cr(VI)-containing compounds.