Patients with active CMV or EBV infection characterized by the presence of specific serum IgM and/or high immunofluorescence in IgG, have higher levels of circulating immune complexes and a lower phagocytic activity of leucocytes than patients with latent CMV/EBV infections or not infected patients. In active infections at the same time the absolute number of lymphocytes with the surface sign CD8 increases. The amount of lymphocytes with differential antigens CD3 and CD4 does not change substantially. Also the levels of the third and fourth component of complement and C-reactive protein remain within the normal range.