During several decades, the Mexican government has sold whole milk at subsidized prices to low income households with children 1-11 y of age through a federal program (Liconsa). In 2000 a decision was made to fortify the subsidized milk with iron, vitamin C and other micronutrients to contribute to the reduction of IDA and other micronutrient deficiencies. At that time, 4.2 million children 1-11 y old from low income families were beneficiaries of the program. There are very few examples of large scale public health interventions using iron fortified whole milk.