Introduction. One of the common methods of treating patients with malignant neoplasms is remote gamma therapy. However, as you know, the blood system is one of the most susceptible to ionizing radiation. The aim of our work was to assess the effect of high doses of gamma radiation with local exposure to blood counts. We analyzed the general blood tests of 51 patients diagnosed with stage I-II breast cancer, who were treated at the Sverdlovsk oncological dispensary. Results and discussion. The greatest changes can be observed in leukocyte counts. After two weeks, 16 (31%) patients had an increase in leukocytes, 35 (69%) - a decrease in leukocytes. Almost all patients (98%) had a decrease in lymphocytes after 2 weeks. After 4 weeks, lymphocytes decreased in all patients. Conclusions. Despite the decrease in indicators by the fourth week, in none of the patients, the level of blood indicators fell to critical values, which indicates the relative safety of radiation therapy in modern conditions for the blood system.