All phases of HPV infection are under the control of the immunitary system which is probably inhibited by the virus itself. We studied 65 patients (range 22-55 year). They presented an HPV vulvovaginal infection not healed after common therapy. The aim of our study was to verify the changes occurring in the immune system during HPV vulvo-vaginal infection. Using the immunohistochemical method we evaluated the number of T4,T8 and NK lymphocytes inside the lesion. Moreover we measured the immunitary cells of the hematic compartment. Inside the lesion we noted a reduction of the immune system in 69.23% of cases, while in the hematic compartment it was reduced only in 6.15% of cases. These data strongly suggested that the evaluation of the immunitary state, before starting therapy, is important in deciding when it would be useful to associate immunostimulating substances at the common treatment of vulvo-vaginal infection.