BACKGROUND: Globally, household air pollution (HAP) is a major environmental hazard that affects respiratory health. However, few studies have examined associations between HAP and lung function decline and respiratory disease and mortality. METHODS: We used data from the Prospective Urban and Rural Epidemiology study and examined adults residing in 240 rural communities in 11 low-and middle-income countries where HAP from cooking with solid fuels is common. Spirometry was conducted for 28,574 individuals at baseline and 12,489 individuals during follow-up (mean of 8 y between spirometry measures). In cross-sectional analyses, we compared lung function measurements [forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1 /FVC ratio] in those who used solid fuels for cooking in comparison with clean fuels. Using repeated measurements of lung function, we examined the percent change in lung function measures per year, comparing individuals by baseline fuel type and individuals who used solid fuels at baseline but switched to clean fuels during follow-up. We also examined associations with prospective health events (any respiratory diseases, respiratory disease hospitalizations, and all-cause mortality). RESULTS: In adjusted cross-sectional models, use of solid fuel in comparison with clean fuels was associated with lower FEV1 of −17:5 mL (95% CI: −32:7, −2:3) and FVC of −14:4 mL (95% CI: −32:0, 3.2), but not FEV1 /FVC. In longitudinal analyses, individuals who switched from solid fuels to clean cooking fuels during follow-up (n = 3,901, 46% of those using solid fuel at baseline), showed no differences in the annual rate of change in FEV1 or FVC, but had small improvements in FEV1 /FVC change (0.2% per year, 95% CI: 0.03, 0.3). Individuals who switched from solid to clean fuels had a decreased hazard ratio for respiratory events of 0.76 (95% CI: 0.57, 1.00) in comparison with persistent solid fuel users, which was not attenuated by lung function measures. CONCLUSION: We observed modest associations between HAP exposure and lung function, lung function change, and respiratory disease and mortal-ity. https://doi.org/10.1289/EHP11179.