The density of minerals and vitamins in food staples eaten widely by the poor may be increased through plant breeding - a process known as biofortification. Biofortification can be accomplished through conventional plant breeding or through use of transgenic techniques. Biofortified crops offer a rural-based intervention that, by design, initially reach these more remote populations, which comprise a majority of the undernourished in many countries, and then extend to urban populations as production surpluses are marketed. In this way, biofortification complements fortification and supplementation programs, which work best in centralized urban areas and then reach into rural areas only in areas with good infrastructure. Initial investments in agricultural research at a central location can generate high recurrent benefits at low cost as adapted biofortified varieties become available in country after country across time at low recurrent costs.HarvestPlus seeks to develop and distribute varieties of food staples (rice, wheat, maize, cassava, sweetpotato, beans, and pearl millet) which are high in iron, zinc, and provitamin A through a global alliance of scientific institutions and implementing agencies in developing and developed countries involved in plant breeding, molecular biology, human nutrition, food science, farm extension, communications, and economics.In broad terms, three things must happen for biofortification to be successful. First, the breeding must be successful – high nutrient density must be combined with high yields and high profitability. Second, efficacy must be demonstrated – the micronutrient status of human subjects must be shown to improve when consuming the biofortified varieties as normally consumed. Third, the biofortified crops must be adopted by farmers and consumed by those suffering from micronutrient malnutrition. Progress in these three areas will be discussed four years into the project.