Globally, nearly 3 billion people rely on solid fuels for cooking and heating, the majority in low- and middle-income countries (LMICs). The resulting household air pollution (HAP) is the third leading risk factor in the 2010 global burden of disease, accounting for an estimated 4.3 million deaths annually, largely among women and young children. The presenters will describe to the audience a large-scale field trial with liquefied petroleum gas (LPG) cookstoves that is aiming at reducing exposure to levels that produce meaningful health improvements. The trial is randomizing 3,200 households in four LMICs (India, Guatemala, Peru, and Rwanda).