Project Summary/Abstract Nearly half of all smokers in the United States have already used electronic cigarettes (e-cigarettes), which are novel devices that deliver nicotine through an inhaled aerosol. Common reasons for use are to reduce or quit cigarettes or to decrease harms from cigarette smoking. The long-term health effects of e-cigarettes are unknown, but because they are widely-available consumer products, understanding their effects on cigarette consumption and short-term health is critical for making decisions about how to counsel smokers about their use. This is particularly important for individuals with chronic lung disease such as chronic obstructive pulmonary disease (COPD), in whom the prevalence of cigarette smoking is more than twice that of the general population. This career development award has two research aims to begin addressing these evidence gaps: (1) To assess patterns and trajectories of cigarette and e-cigarette use in a nationally-representative longitudinal cohort of smokers with COPD, and (2) To test, in a pilot randomized trial, whether providing e- cigarettes for 12 weeks to cigarette smokers with mild to moderate COPD who do not plan to quit cigarettes in the next month reduces their daily cigarette consumption. Secondary outcomes include changes in tobacco biomarkers, FEV1, dyspnea, and quality of life over 12 weeks. This research plan is complemented by a training program and highly expert team of mentors, collaborators, and advisors that will provide further training in large dataset and longitudinal data analysis, clinical trial design and conduct, and pulmonary medicine. The career development award will equip me with the skills to become an independent investigator conducting population studies and clinical interventions of nicotine and tobacco use. It will prepare me to submit an R01 proposal to conduct a fully-powered randomized controlled trial of the effect of e-cigarettes on cigarette smoking and respiratory symptoms and function in smokers with COPD.