Interleukin-2 (IL-2) is a cytokine produced by lymphocytes T CD4+, T CD8+ and NK cells. IL-2 increases the number of lymphocytes T and prolongs their survival and has extensive immunomodulatory effect. High levels of IL-2 are observed during asymptomatic phase of HIV infection (TH-1 dependent cytokine) and low levels are observed during progression of immunodeficiency. IL-2 inhibits apoptosis of CD4+ T cells, improves NK cells activity, has influence on production of soluble antiviral factor (CAF) which inhibits viral activity etc. That is why IL-2 has been introduced to the treatment of HIV infection along with highly active antiretroviral therapy (HAART). High T CD4+ cells count predicts long survival of HIV infected individual. Phase III clinical trials concerning IL-2 are now performed and the preliminary results are promising. Polish centers also take part in the ESPRIT study. Adverse events of various severity are seen in patients under treatment (anti inflammatory drugs are required). The symptoms usually resolve within a few days after IL-2 therapy is stopped.