The study is a multicenter, prospective observational study of pathogenesis of HIV pulmonary disease. We will determine the prevalence and risk factors for lung dysfunction as quantified by pulmonary function testing in HIV+ subjects. We will build on our existing longitudinal cohorts while adjusting for important co-variates such as antiretroviral therapy (ART), smoking history, co-infections, and illicit drug use. Evaluations will be scheduled at baseline, 18 months, and 36 months. (6, 12, 18 and 36 months for ART initiators at the UCSF). Study visits will consist of blood draw, questionnaires, pulmonary function testing, 6-minute walk test, CT of the chest at visit two. Oral specimen collection and glycocalyx and echocardiogram (visit two) at the Pittsburgh site only.