We present the results from a study of 97 female blood donors who reappeared for donation after giving birth from nine to 60 months before. The donors answered a questionnaire about number of pregnancies, the time since last pregnancy, iron medication before and during pregnancy, and methods of contraception. Serum ferritin was determined in a blood sample drawn before donation. In this group, mean serum ferritin was 21.5 +/- 14 micrograms/l. In a control group consisting of young women who registered as donors the mean serum ferritin was 39.4 +/- 29.4 micrograms/l. There was a decrease in serum ferritin with increasing age and parity. The mean serum ferritin value was higher among women who had taken iron supplements regularly before and during pregnancy than among women who had not taken iron supplements. The differences were statistically significant for iron supplementation during pregnancy. Iron supplements during pregnancy seem justified, but further information should be obtained about necessary does and appropriate time for starting supplementation.