The absorption of nonheme iron from nine common Western type breakfasts was studied in 129 subjects using extrinsic labeling with radioiron. In one group the iron absorption from a continental type of breakfast served with coffee was standardized against the absorption from a reference dose of derrous ascorbate (3 mg Fe). In all subsequent experiments the absorption from this breakfast was compared with one of the other breakfast meals served on alternate days and each labeled with a different radioiron isotope. The bioavailability of iron in the different breakfast meals varied markedly. There was almost a 6-fold idfference in absorption (0.07 to 0.40 mg) despite of the fact that the iron content only varied from 2.8 to 4.2 mg. The most marked effect was seen with tea which reduced the absorption to less than half and with orange juice which increased the absorption two and a half times. The present findings must be considered when giving dietary advice to groups of subjects who are known to have a critical iron balance. The present results also imply that an evaluation of the iron nutrition in a population cannot only be based on the daily dietary intake of iron but must also include the bioavailability of iron in frequently consumed meals.