Lung cancer incidence is substantially elevated among people infected with human immunodeficiency virus (HIV). Although frequent smoking may partly explain this increase, recent work suggests other factors may also be involved. To better characterize smoking habits and lung cancer risk in HIV-infected people, the investigators propose a cross-sectional pilot study of HIV-infected and uninfected injection drug users in the ALIVE cohort in Baltimore, Maryland. A detailed questionnaire on smoking behaviors and other lung cancer risk factors will be administered to all ~ 1600 cohort subjects. In addition, the investigators will measure serum cotinine (a marker of recent smoking intensity) for a sample of 340 African American males from the cohort, stratified on the amount of cigarette use, HIV status, and CD4 count. Spirometry will be performed on the entire group of 1600 subjects, to assess for chronic obstructive pulmonary disease. Differences between HIV-infected and uninfected subjects in smoking habits, exposure to tobacco, or lung damage will identify areas for future investigation.