Iron supplementation remains an important strategy for the prevention and treatment of iron deficiency anemia and can produce substantial improvements in the functional performance of iron deficient individuals and populations. Many potential benefits of iron supplementation require further exploration, including its effect on vitamin A and iodine metabolism. There is strong evidence that vitamin A and riboflavin deficiencies affect iron utilization from supplements and are important on a global scale, but little evidence that folate and vitamin B-12 deficiencies play a major causal role in the global burden of anemia. The efficacy of multiple micronutrient supplements for the prevention and treatment of anemia must be further evaluated. Because weekly supplementation with iron is effective at improving iron status, this option should be thoroughly explored and evaluated in the context of programs for the prevention and the treatment of iron deficiency and anemia. More conformation is warranted concerning the number of tablets that must be consumed in different situations, and the efficacy of supplying other micronutrients weekly with iron. Weekly supplementation programs may improve the logistical and economic constraints that currently limit the provision of supplements to the many target population groups for whom they are recommended, but usually fail to reach. Further work is required to clarify the purpose, delivery and outcomes of iron supplementation programs.