Inefficient cooking and heating with solid fuels in poorly ventilated homes are a major source of exposure to indoor air pollution in developing countries. Household air pollution from cooking and heating with solid fuels also is an important contributor to outdoor air pollution. The combustion of organically derived solid fuel is qualitatively similar to the burning of tobacco in terms of emissions of particulate matter and gases, and the mechanisms by which solid fuel smoke causes adverse health effects in human subjects are likely similar. The public health effect of domestic cooking and heating with solid fuels is great. The World Health Organization estimates that there are 3.8 million deaths globally per year attributable to household air pollution. This estimate is based on the strength of the evidence, primarily meta-analyses of epidemiologic studies of acceptable scientific quality, although for cardiovascular disease, the evidence is more inferential. The greatest burden of household air pollution–related premature deaths is in children with pneumonia exposed to biomass smoke. The greatest estimated burden in adults is cardiovascular disease, but chronic obstructive pulmonary disease and lung cancer are important causes of disability and premature death in women, who are the primary cooks and tend not to smoke tobacco in developing countries. Research gaps and opportunities for interventions to reduce effects of solid fuel smoke on public health are identified.