Aims To investigate dexamphetamine transfer into milk, infant doses and effects in the breast-fed infant.Methods Four women taking dexamphetamine, and their infants were studied.Results The median maternal dexamphetamine dose was 18 mg day(-1) (range 15-45 mg day(-1)). Median (interquartile range) descriptors were 3.3 (2.2-4.8) for milk/plasma ratio, 21 mu g kg(-1) day(-1) (11-39) for absolute infant dose and 5.7% (4-10.6%) for relative infant dose. No adverse effects were seen. In three infants tested, dexamphetamine in plasma was undetected in one (limit of detection 1 mu g l(-1)) and present at 18 mu g l(-1) and 2 mu g l(-1) in the other two.Conclusion Dexamphetamine readily transfers into milk. The relative infant dose was <10% and within a range that is generally accepted as being 'safe' in the short term.