Ischemic stroke is the most common form of brain stroke. It is associated with functional changes of various blood and bone marrow cell populations, altered release of various cytokines, chemokines, etc. There are conflicting data about serum and plasma TNFα levels in acute ischemic stroke.We have examined 21 patients with a diagnosis of ischemic stroke treated at the hospital. The severity of ischemic stroke was evaluated by neurologists, in accordance with NIHSS criteria at admission and at discharge. In the patients with ischemic stroke, we have found a significantly increased serum concentration of tumor necrosis factor-α (p < 0.001), as compared with healthy individuals. The highest concentrations of this marker were recorded on days 1 and 3 of the disease, being significant at p < 0.001 and p= 0.003, respectively, then decreasing by day 14, however, not reaching, the levels of control group. It should be noted that, among patients with ischemic stroke, there is a significantly (p < 0.001) increased proportion of individuals with high serum concentrations (>10 pg/ml) of this cytokine, i.e., 76.2±9.3% on day 1 of the disease.To statistically evaluate the individual differences of the patients’ dynamics, they were divided into subgroups, depending on the level of TNFα on the 1st day of hospitalization, using a discriminant analysis with estimation of a classification matrix. The correlation analysis showed numerous strongly positive correlations between TNFα levels on the 1st and 3rd days, as well as between similar indexes on the 1st and 14th days. A correlation between TNFα concentrations on the 3rd and 14th day was also found (r = 0.711; p < 0.01). Also, positive correlation in various periods of observation was established between the absolute levels of cytokine and differences in their concentration changes. The level of tumor necrosis factor-alpha on the first and third day of hospitalization did positively correlate (respectively, r = 0.503, p < 0.01; r = 0.411, p < 0.01) with the volume of the ischemic lesion according neuroimaging methods research. The volume of the ischemic focus was positively correlated with the difference in the concentration of TNFα on days 1-3 and 1-14 (respectively, r = 0.425, p < 0.01; r = 0.507, p < 0.01).The results of our study show a necessity for measuring TNFα levels at admission, in order to plan treatment in these groups of patients, especially in cases of increase or insufficient decrease in TNFα recorded on the 3rd day of therapy.