The immunocompromised state is a major risk factor for the development of malignant tumors. Individuals with human immunodeficiency virus (HIV), and acquired immunodeficiency syndrome (AIDS) represent a large segment of the immunocompromised group of patients. Kaposi's sarcoma, B-cell non-Hodgkin's lymphoma, primary central nervous system lymphoma, and invasive cervical carcinoma are malignant tumors that are all AIDS-defining illnesses. Lung cancer is also seen with a higher frequency in AIDS patients. Malignant tumors are more aggressive in this group of patients as compared with the general population. Prognosis is poor, although with the improved survivals seen with new treatment in these patients, aggressive therapy is still warranted.