A comparative analysis of the frequency of cytogenetic abnormalities in cell population U-937 in control conditions and after exposure to tumor necrosis factor has been performed. We have found that in such treatment there is a maximum effect after 48 h, which is expressed in the stimulation of apoptosis and the accumulation of cells with micronuclei and binuclear cells. The induction of premature chromosome condensation is an early marker of the TNF influence. Changing the composition of the population by the number of chromosomes in the cell may lead to the emergence of a subline with new properties compared to the parental cell population.