Air pollution in big cities gets headlines, but in many rural areas of developing countries indoor air pollution is an even more serious health problem. Long-term exposure to smoke from cooking indoors with wood, animal dung, and other biomass fuels contributes to respiratory illness, lung cancer, and blindness. As a cause of ill health in the world, indoor air pollution ranks behind only malnutrition, AIDS, tobacco, and poor water/sanitation. The results of a national household survey in India linking cooking smoke to tuberculosis and blindness in adults and acute respiratory infections in children add to a growing body of evidence from other studies that reducing exposures to toxic emissions from cookstoves can substantially improve health and save lives. Governments can do more to promote clean fuel use, educate people to the risks of exposure to cook smoke, and provide and promote more efficient and better-ventilated cookstoves. Curbing indoor air pollution is not only a key to better health but also an important investment for achieving development goals and improving living standards.