At study entry, patients receive a comprehensive physical exam. Clinic staff interview the patient to collect data regarding medication history (particularly antiretroviral exposure), diet, occupational history, substance abuse, and sexual practices. This information is used to identify behavioral and environmental factors contributing to oncogenesis. In addition, baseline blood samples are analyzed for HHV-8 and EBV levels, anti-EBV and anti-HHV-8 antibodies, CD23, Th2 cytokines, tumor growth factors, chromosomal translocations associated with NHL, and other potential predictors of malignancy. At Month 6 and annually thereafter, patient records are abstracted for data on vital status, AIDS-defining illnesses, medications, and most recent CD4+ T cell and HIV RNA levels. At Years 1, 2, and 3, patients undergo physical exams and blood tests for malignancy surveillance. Any malignancies are biopsied and analyzed for oncogene identification and virology. The medical records of patients who die on study are reviewed to determine the cause of death and to rule out unreported cancer. No treatment is provided by this study.