Serum ferritin and haemoglobin rate were assessed in 637 men and 285 women, all of them seemingly healthy, who were about to donate blood for the first time. Serum ferritin rates suggesting iron deficiency were found in 1.88% of the men and in 9.47% of the women, anaemia being present in 7.69% of the iron deficiencies. Serum ferritin can be a useful parameter for the detection of latent iron deficiency in blood donors, and it may disclose the group of donors who should receive iron therapy, or should be recommended not to donate blood, without any significant increase on the cost per unit of blood.