Recent studies have described a reduced incidence or the regression of Kaposi's sarcoma (KS) in HIV-infected patients treated with the highly active anti-retroviral therapy (HAART) that contains at least one inhibitor of the HIV protease (HIV-PI) such as Indinavir. Experimental studies have shown that part of the anti-KS actions of HIV-PI are not related to their antiretroviral actions, but, at least in part, to their capability of blocking angiogenesis and tumor growth.