This experimental study was designed to investigate the effects of daily versus intermittent iron supplementation on iron status of high school girls in Zahedan and Rasht cities in 1996-1997. The subjects were selected randomly from among students of grades 1-3 of four high schools in each city. Anemia was determined by measuring hematological indices. 260 anemic and a similar number of non-anemic subjects of 4 high schools were selected and allocated randomly to 4 treatment groups. During a 3-month period, the test groups were given 150 mg ferrous sulfate tablets (50 mg Fe). Subjects in group 1 received a daily dose, groups 2 & 3 received twice or once weekly doses respectively. The control group received no iron supplement. For these subjects, in addition to hematological indices biochemical iron indices were measured in the beginning and at the end of the study. The increases in hemoglobin concentration in anemic subjects were not significantly different among supplemented groups but were different from the control group (p < 0.00001). Among anemic subjects, changes in serum ferritin levels in 3 supplemented groups were significantly different from the control group. Serum ferritin in Group 1 was also increased to a greater extent than groups 2 and 3 (P < 0.00001). It is concluded that over the study period a weekly iron dose was as effective as a daily dose in treating anemia but the daily dose was more effective in improving iron stores than a weekly dose in the short run.