Background: The incidence of lung cancer is quite high among people with the human immunodeficiency (HIV) virus. Frequent smoking may explain that cancer increase, given that 50% to 70% of HIV-infected people are current smokers. Recent research suggests that other factors may be involved as well. Smoking habits, such as smoking earlier in life or smoking more cigarettes a day than others do, may have a role. Also, HIV-infected smokers seem to have a greater risk of chronic obstructive pulmonary disease (COPD). The association of HIV and COPD is important, because COPD itself is linked to an increased risk of lung cancer. About 1,600 subjects from the study known as ALIVE (AIDS Linked to the Intra-Venous Experience), which began in 1988 in Baltimore, Maryland, will be given a detailed questionnaire on smoking behaviors and lung cancer risk factors. They will also have spirometry testing, to evaluate lung function. Objectives: To better characterize smoking habits and compare tobacco use among HIV-infected and uninfected drug users. To compare serum cotinine levels and spirometry results, as a marker of tobacco use and a marker of damage to lung function, respectively. Eligibility: Patients 18 years of age and older who are in the ALIVE cohort. Design: Patients undergo the following procedures: - Completing a questionnaire on smoking history. Questions include age when smoking began, periods of quitting smoking, average number of cigarettes per day for specific periods, amount of each cigarette smoked, depth of inhalation, type of cigarette, nicotine dependence, use of other smoked [Note: I would not mention that these drugs are illegal] drugs, exposure to environmental tobacco smoke, past medical history, and recent respiratory symptoms. - Spirometry testing. Patients are asked to breathe as deeply as possible and then rapidly exhale into a tube. The forced expiration volume in 1 second reflects the average flow rate during the first second, and it can be used to determine the degree of pulmonary obstruction. - Blood samples. Tests measure levels of cotinine, a chemical made by the body from nicotine. African American males, who constitute the majority of the ALIVE cohort, participate in this test. Results would show how much tobacco smoke has recently entered the body. For this test, researchers plan to evaluate 240 current tobacco smokers and 100 participants who report no recent cigarette use.