We have retrospectively studied 35 cases of Kaposi's sarcoma in 460 patients with AIDS (incidence of 7.6%) during a period of 10 years. All of them were males, with a mean age of 38 years. 88% of the cases belonged to the homosexual risk group. The tumor was the diagnostic criteria of AIDS in 25 patients. At the moment of the diagnosis, 4 patients were at stage I, 23 at stage II, 1 at stage III and 7 at stage IV, according to the Mitsuyasu's classification; 7 patients had systemic symptoms. The tumor was localized at the skin (34 cases), mucosa (16), digestive tract (7), lung (6) and ganglion (4). The immunological study revealed lymphopenia in 74% of patients, reduction of T4 lymphocytes ( < 0.5 x 10(9)/L) in 93% and inverted T4/T8 ratio in 96%. Sixteen patients received antitumoral treatment (8 with chemotherapy, 7 with interferon and 5 with radiotherapy). The response was stabilization of lesions in 8 cases, partial remission in 2 and progression in 3; in other 3 cases, such response was not assessed. The mortality was 48% and the average survival, 13 months. Opportunistic infections were the cause of death in most patients. Our results confirm the clinical and evolutive characteristics of the Kaposi's sarcoma associated to AIDS; disseminated cutaneous affectation with frequent visceral affectation, poor response to treatment and low survival associated to the presence of opportunistic infections. The lower incidence of tumor observed in our study is related to the different distribution of the risk groups for HIV in our country.