Whether immunomodulators may be used not only to treat immunodeficiencies, but to prevent infectious diseases has been under general discussion in the past years. The use of immunomodulators is mostly substantiated and promising in preventing polyetiological infections (e.g. acute respiratory diseases) against which there are not available specific preventing agents (vaccines) or the latter, if available, are ineffective. This has been evidenced by controlled epidemiological tests that show the potential and actual efficiency of immunomodulators as agents of nonspecific prevention of infectious diseases. The basic lines of studies, which make it possible to elaborate the tactics of drug use, based on the definition of epidemic indications and on the choice of the optimal preventive measures, are substantiated.