Serum ferritin was determined in 170 healthy Norwegian women (18-48 years; median age 36 years) including 23 blood donors. In women with serum ferritin less than or equal to 20 micrograms/l haemoglobin, serum iron and total iron binding capacity were determined. Women using oral contraceptives were excluded. Information was collected on use of contraceptive techniques, habits of iron prophylaxis, and duration of menses. About 40 per cent of the participants used the intra-uterine device. Geometric mean serum ferritin was 26.9 micrograms/l with a prevalence of 21.8 per cent with exhausted iron stores (serum ferritin less than 17 micrograms/l) among the non-donors. In the group with low to empty iron stores (serum ferritin less than or equal to 20 micrograms/l) 13 per cent had anaemia (Hb less than 120 g/l). This may correspond to 4.1 per cent among all the non-donors. The blood donors had a geometric mean serum ferritin of 20.4 micrograms/l and 30 per cent with empty stores. Our study shows that in the group of non-donors there was a tendency to higher prevalence of low or empty iron stores among IUD-users and premenopausal women. In addition to these groups the blood donors are at risk of iron deficiency.