Nitrate pollution of groundwater has been increasing in recent years. The aim of this work was to study the morphological features of the bone marrow of rats at the consumption of drinking water with varying nitrate content. The experiment was performed on 2 groups of white female rats of different ages (mature and immature) with 30 individuals each. Both groups were divided into 5 subgroups that differed in the quality of drinking water consumed by rats on their own. In the 30 days study, nitrate was given to rats in drinking water in doses of 50, 150, 250, 500 mg of sodium nitrate per liter. Animals of the control group drank water from the city water supply. The effect of nitrates on the bone marrow of rats was evaluated by morphological analysis. It was found that the consumption of drinking water with nitrates affected erythropoiesis and leukopoiesis, as evidenced by the growth of blasts, lymphocytes, pronormocytes and normocytes, megakaryocytes and eosinophils, displacement of erythrocyte sprout cells. An increase in the neutrophil maturation index indicates delayed neutrophil maturation, increased yield of mature cells from the bone marrow and depletion of the granulocyte lineage. The more pronounced changes were observed in the qualitative and quantitative composition of the components of the erythrocyte sprout. These disorders were dose-dependent with increasing hematotoxic effect of nitrates at doses of 250 and 500 mg/l in the group of immature animals and resulted in changes in the bone marrow, which may further cause the development of pathological processes in an organism. Keywords: bone marrow of rats, drinking water, nitrates, Van Gieson’s stain