Understanding the rate of lymphocyte replication and destruction in HIV infected patients, as well as the effects of therapy on lymphocyte replication should lead to a better understanding of the mechanisms behind the immunodeficiency induced by HIV. To examine this directly, up to 85 HIV-infected patients will be enrolled in the study. Patients will receive up to two 30 minute infusions (at least one month apart) of bromodeoxyuridine (BrDU; 200 mg/m(2)), an analogue of thymidine. BrDU is incorporated into DNA and can be measured using an anti-BrDU monoclonal antibody. It can be measured in subpopulations of cells to determine the rate of replication of those cells. All participants in this study will be reimbursed for the inconvenience and discomfort associated with study participation.