Comparative analysis of changes in hematological parameters of hens under short-term exposure to various negative environmental factors was performed. For this purpose in the conditions of a modern complex on production of food eggs 3 groups of hens were formed, each of which was kept in a separate cage-analogue on the area and the equipment. In particular, the hens of the 2nd group were deprived of fodder, the 3rd group – of light, and the 4th group – were kept with a significant overcrowding. Exposure to the factor in all groups was 24 hours, after which hematological parameters were determined. Differences in the response of the blood system of hens to short-term exposure to adverse environmental factors depending on their nature were found. The smallest changes in the blood system of hens were observed under the influence of the lack of food, namely an increase, within the physiological norm, the content of leukocytes and ESR, decreased hemoglobin, hematocrit, erythrocytes, platelets, as well as violation of the ratio of different forms of leukocytes – an increase in the concentration of heterophiles (3.3% > normal) on the background of a decrease in the concentration of monocytes (1.6% < normal), lymphocytes and basophils. Whereas under the influence of the factor of lack of light, a higher content of leukocytes in the blood by 10.6%, a lower concentration of hemoglobin by 22.4%, hematocrit – by 4.2%, platelets – by 9.8%, as well as higher erythrocyte sedimentation rate by 9.8%, higher concentration of heterophiles by 5.9% and lower concentration of lymphocytes – by 4.6%, compared with the lack of food. The most significant changes in the blood system were observed under the influence of a factor of significant overcrowding of hens, namely higher blood leukocytes by 17.1 and 5.9%, lower hemoglobin concentration by 29.6 and 9.2%, hematocrit – by 5.9 and 1.7%, erythrocytes – by 10.3%, platelets – by 35.8 and 28.8%, as well as higher erythrocyte sedimentation rate by 4.9%, higher concentration of heterophiles by 11.3 and 5.4% and lower concentration monocytes – by 0.8 and 0.4%, lymphocytes – by 9.4 and 4.8% and eosinophils – by 0.7%, compared with the factor of lack of food and lack of light, respectively.