To determine the effect of pre-existing filarial infection and its treatment on viral burden and clinical parameters in patients infected with HIV, this study aims to follow plasma HIV loads, CD4 counts, and clinical parameters in a population of HIV-infected individuals co-infected with Wuchereria bancrofti, prior to and after treatment of filarial infection. The study individuals will be drawn from the patient cohort followed by the HIV Clinic at the Government General Hospital and the Tuberculosis Research Centre, Chennai, India, or those from YRG-Care (Chennai, India), an area endemic for lymphatic filariasis (LF) and where the prevalence of HIV infection in the general population is about 7%. These patients are adults of all ages, both males and females, come from the states of Tamil Nadu and Andhra Pradhesh. Having established as part of a previous protocol (01-I-N022) an HIV/filarial coprevalence of 6-10% based on W. bancrofti circulating antigen detection in HIV-positive and -negative individuals, patients in whom co-infection with HIV and LF has been diagnosed will be paired with two HIV-positive (but filarial antigen negative) clinic controls matched for age, gender, viral load antiretroviral therapy and CD4 count. All efforts will be made to connect study participants with programs for antiretroviral distribution. Within a month of a baseline clinical evaluation, patients and controls will receive a single dose of the combination of diethylcarbamazine/albendazole (the drug combination given as part of national campaigns to eliminate LF) and will then be followed with viral loads, CD4 counts and clinical examinations at one week, as well as 1, 3, 6 and 12 months after the administration. By assessing these changes, the influence of a co-existing filarial infection on plasma HIV viral load, CD4 count and clinical course can be determined. At the end of the study period, all participants will be re-assessed for filarial antibody and antigen to ensure absence of the parasite. Any patient who has evidence of ongoing filarial infection with W. bancrofti will be re-treated with DEC/albendazole.