In Vietnam the high prevalence of iron deficiency anaemia in infants and young children speaks for implementing early interventions. This study aimed to evaluate the efficacy of the daily iron supplementation in infants given by their mothers and of the weekly iron supplementation. Two hundred and seventy infants aged 5 to 12 months, were divided into four groups. Group 1 received a placebo daily and group 2 a daily dose of 15 mg iron (2.0 +/- 0.3 mg iron/day/kg body weight) which was given by their mothers for three months. Group 3 received a daily dose of 15 mg iron and group 4 a weekly dose of 15 mg iron given during 6 months by health auxiliaries. The hemoglobin concentration (Hb) was measured before the intervention and after 3 months of supplementation in all groups, and again after 6 months of supplementation in groups 3 and 4. After 3 months of iron supplementation, the hemoglobin concentration increased significantly by 21.6 +/- 12.3 g/l and the prevalence of anaemia decreased from 81.3% to less than 9% in group 2. The weekly iron supplementation was significantly less effective than the daily supplementation: after 3 months, Hb increased by 15.4 +/- 13.3 g/l in group 3 and by 11.2 +/- 10.2 g/l in group 4 (p = 0.04) and the prevalence of anaemia was 17.9% and 41.5% in groups 3 and 4, respectively. After 6 months of supplementation, changes in Hb were not significantly different between group 3 (22.0 +/- 12.1 g/l) and group 4 (20.0 +/- 10.0 g/l, p = 0.30). However, the final hemoglobin concentration was significantly lower in group 4 (120.5 +/- 7.2 g/l) than in group 3 (123.6 +/- 7.8, p = 0.02). Moreover, nearly 8% of the children were still anemic in group 4 versus 0% in group 3. Since the early developmental period, when the brain and other specific organs are especially sensitive to iron deficiency, is critical, 3-month daily iron supplementation of infants from the age of 6 months has to be recommended, followed by a weekly iron supplementation until the age of 15 months. The community approach, where mothers informed on the importance of iron deficiency anaemia and on the consequences for the health of their infants gave the iron supplements, was shown to be effective. However, its sustainability would depend on the availability of low-cost iron supplements affordable by populations with limited economic resources. Other interventions, such as iron supplementation of women during fertile age, especially during pregnancy and lactation periods, and the use of complementary food to breast milk, fortified with micronutrients, should be associated.