Antibodies to cytomegalovirus class IgG and IgM and level of tumor necrosis factor (TNF) in the serum were measured in 81 patients with severe surgical infections. In patients with acute lung abscess TNF level was twice higher and activation of cytomegalovirus infection (specific IgM) was three times more frequent than in patients with infectious endocarditis. The conclusion is made that severe surgical infections inducing progressive immunodeficiency create conditions for activation of latent viral infections, cytomegalovirus, in particular). Recommendations on prevention of hemotransmissible cytomegalovirus infection are presented.