The aim of this study was to estimate the frequency of HSV and/or CMV among the pathogens causing intrauterine infections (IUI) and to investigate their impact on the level of proinflammatory cytokines in premature neonatal infants. Examinations were performed in 3 neonatal groups: 1) premature neonates with clinical manifestations of IUI; 2) those without IUI; 3) full-term newborns. In group 1, viral (HSV and/or CMV) and bacterial infections were detectable with the same frequency. Quantitative analysis of plasma IL-6 and IL-8 levels and the induced production of these cytokines by blood cells in vitro showed that in Group 1 neonates, IL-6 and IL-8 concentrations were substantially higher and the induced production of these cytokines was lowerthan those in Group 3. The detection of HSV and/or CMV markers in premature newborn infants was attended by a statistically significant rise in plasma IL-6 levels; the identification of the opportunistic bacterial microflora correlated with the higher concentration of IL-8. In Group 1, wiferon produced an immunomodulatory effect, by lowering IL-8 concentrations to the level observed in Group 3.