To accomplish the overall goal of providing evidence necessary to evaluate the impact of reducing exposure to biomass smoke on lung function decline, we are building on the infrastructure of the Cooking Stove and Pneumonia Study (CAPS) randomized controlled trial (RCT) of the Philips gasifier stove for the prevention of childhood pneumonia and a cross-sectional Burden of Lung Disease (BOLD) study of adult respiratory health in rural Malawi. In CAPS, approximately 3,600 households have been recruited from 50 villages in the Chikhwawa district using a cluster randomization approach at the village level. The CAPS protocol has been reviewed and published by the Lancet. For the BOLD study, 2,000 men and women in two age strata (18-39 and ≥40) are currently being recruited from the villages participating in CAPS. We plan to follow the BOLD participants annually for 6 years to assess personal exposure (PM2.5, CO, and BC), lung function, and respiratory symptoms. In addition, because ~50% of the 2,000 participants to be recruited for the BOLD study will be from CAPS households, we will be able to conduct an RCT of the efficacy of the Philips stove in this nested sub-cohort.