Kaposi's sarcoma (SK) is a cutaneous disease mostly affecting elderly men of Mediterranean ancestry, people from sud-Saharan Africa and HIV infected patients. It is a proliferation of spindle cells. It's neoplastic origin remains controversial. Infection with a gamma herpes virus HHV8 is necessary for the development of KS. In organ recipient patients KS is observed and seems to be related to immune deficiency. In HIV infected patients an effect of HIV as a promoter on KS is added to immune deficiency. Half of HIV-HHV8 co-infected patients may develop KS. Therapeutic management of HIV infected KS patients is primarily to treat HIV infection. This treatment contributed to a dramatic decrease of KS incidence in developed countries. When antiretroviral treatment failed, conventional chemotherapy can be used. New therapies taking in count the complex mechanisms of the KS genesis are under evaluation.