The object of the present invention relates to the new and surprising use of sulfated hyaluronic acid (HAS) as regulator agent of the cytokine activity (pro- and antiinflammatory) and consequently the use of HAS for the preparation of a new medicine for the prevention and treatment of pathologies associated with the activation and/or deficiency of cytokines of a pro- and antiinflammatory nature. The Applicant has in fact discovered its exclusive capacity in modulating the activity of these particular proteins, it has studied the action mechanism and demonstrated the substantial difference between the different sulfated types known in the state of the art, but above all it has demonstrated an unexpectedly high activity of HAS vs different types and strains of Herpes virus, HIV, Cytomegalovirus and the virus of vesicular stomatitis.