This 7-mo double-blind study compared the efficacy of two iron supplementation schemes in improving iron nutrition among 116 healthy fertile-age women. They were randomly distributed in three groups, receiving: Group 1, iron + folate (60 mg and 250 microg, respectively) daily for 3 mo (currently recommended scheme), and folate (250 microg) weekly the subsequent 4 mo. Group 2, folate daily, and 60 mg iron only once weekly for 3 mo, and then weekly iron + folate for 4 mo. Group 3, folate daily for 3 mo and then weekly for 4 mo. At baseline, 16% had depleted stores (plasma ferritin <15 microg/L) and 16% had hemoglobin levels <125 g/L. Eight percent had hemoglobin levels <120 g/L. In Group 1 hemoglobin and ferritin increased at 3 mo but returned to near basal conditions after 4 mo of weekly folate. In Group 2, hemoglobin and ferritin increased progressively throughout the 7 mo but mostly after 3 mo. Group 3 did not change. Side effects were highest with daily iron. Weekly iron supplementation over 7 mo (30 doses) improved and sustained iron nutrition at least as effectively and was better tolerated than 90 daily iron supplements consumed during 3 mo.