The chromium concentration was determined in 261 samples of breast milk collected by manual expression from forty-five American women. Cr was measured in whole, liquid milk by graphite-furnace atomic absorption spectrophotometry, using the method of standard additions. The mean Cr content of the breast milk samples was 0.30 ng/ml. The range of individual values was 0.06-1.56 ng/ml and did not change significantly with duration of lactation. The Cr content of breast milk from these American women is similar to levels reported recently in milk from Finnish women.