Dirty cooking fuels are a significant source of indoor air pollution in developing countries, resulting in millions of premature deaths. This paper investigates the health impacts of household access to cleaner fuel using a nationwide fuel-switching program, the largest household energy transition project ever attempted in the developing world, affecting more than 50 million homes in Indonesia. This program focused on replacing a dirty cooking fuel (kerosene) with a cleaner one (liquid petroleum gas). The difference-in-differences estimates and within-mother estimates suggest that the program led to a significant decline in infant mortality with the effects concentrated on the perinatal period. The program also reduced the prevalence of low birth weight, suggesting that fetal exposure to indoor air pollutants is an important channel. These findings elucidate how a policy that combines a subsidy on the use of cleaner-burning fuel with a restriction on the dirty fuel can pay public health dividends.