The Italian Cooperative Group on AIDS-related tumors has collected 435 cases of HIV-associated tumors since December 1986. The following conclusions can be drawn from this IVDA-based series: (1) at least 15% of AIDS cases are associated with tumors; (2) the number of malignant lymphomas (high-grade non-Hodgkin's lymphoma [NHL], Hodgkin's disease [HD] is comparable to that of Kaposi's sarcoma (KS) (188 vs. 198); (3) KS among AIDS patients is less common than in countries where homosexual men are the main group affected by AIDS. However, KS also affects intravenous drug abusers (IVDA) almost exclusively males, with characteristics similar to those observed among homosexual men; (4) HD is associated with an aggressive course; (5) anal and oral primary tumors as well as oral and anal involvement of NHL are very rare; (6) testicular cancers occur in patients mainly with early HIV infection, without adversely affecting the dosage of radiotherapy and chemotherapy; (7) cervical cancer successfully treated with conization suggests that PAP test screening in young IVDA women is warranted; (8) lung cancer occurs in a young age group with rapid progression and death.