In pursuing its mission of improving health in the developing world, Population Services International (PSI) is a leading promoter of family planning, oral rehydration therapy, malaria and HIV prevention, and safe water. It is a major provider of long-lasting insecticide treated bed nets and condoms. PSI devotes great attention to assessing the impact of its efforts, using metrics such as years of healthy life added. In advance of a possible movement of its programming into provision of improved cookstoves and hence reduction of indoor air pollution, a major killer globally, PSI and the Pardee Center are collaborating on an impact assessment of such stoves, an outgrowth of the work of the Center in health forecasting.