Differences between feeding practices in earlier investigations prompted the present study of iron and vitamin E supplementation in breast milk fed preterm infants. A new and highly sensitive technique for quantitation of alpha-tocopherol in serum was used. Studies on 34 infants with a birth weight below 2000 g or gestational age less than or equal to 35 weeks showed that supplementation with 16.5 mg tocopheryl acetate/day from 10 days of age resulted in a significantly higher haemoglobin concentration and lower reticulocyte count at 8-10 weeks than supplementation with 1.5 mg/day (p is less than 0.05). Studies on 23 infants with a birth weight of 2000-2499 g revealed subnormal alpha-tocopherol levels in 2 of the infants given 1.5 mg tocopheryl acetate/day but there was no effect on the haemoglobin concentration at 8-10 weeks. There were no untoward effects of an early iron supplementation with 2-3 mg Fe++ (as ferrous succinate)/kg/day. It is concluded that extra supplementation with vitamin E is advisable also in breast milk fed preterm infants. A low dosage iron supplementation from 3 weeks of age is safe.