Less frequent iron supplementation may be equally as beneficial to Fe-deficient subjects as routine daily supplementation because of the short-term suppressive effect of oral dosing with large amounts of Fe on subsequent Fe absorption. In the present study, the possibility that the administration of an Fe supplement every 2nd or 3rd day may be as effective in improving Fe status as a daily supplement was investigated in anaemic rats. Anaemic rats were given a 4 mg Fe supplement every day, on alternate days or every 3rd day, as a single dose with a midday meal or as a multiple dose with a morning, midday and evening meal. A low-Fe diet (13 mg/kg) was given at all other times. After 7 d, erythrocyte count, packed cell volume, mean cell volume, haemoglobin concentration and total liver Fe were measured and compared with those of meal-fed rats which had not been given any supplemental Fe. Rats which received a supplement every 3rd day, a total supplement of 12 mg, had a similar Fe status to those receiving a daily supplement, a total supplement of 28 mg. Administration of the supplement as a multiple, rather than as a single dose did not improve recovery from the Fe deficiency. It is suggested that less frequent supplementation with a smaller total amount of Fe, should be considered in human subjects. Such a regimen would minimize unpleasant side-effects of oral Fe therapy, decrease the risk of adverse effects of Fe on the absorption of other essential minerals and substantially cut the cost of supplementation programmes.