(1) Report of severe adverse effects in infants from drugs passing into breast milk are rare. (2) Two reports of neurological disorders in infants due to doxepin, a tricyclic antidepressant, necessitating hospitalisation, serve as a reminder that this risk exists. (3) Epidemiological data are almost non existent. A prospective follow-up study of more than 800 breast-fed infants whose mothers were taking medicinal drugs showed minor adverse effects in 11% of the children (mainly diarrhoea, drowsiness and irritability). None of the mothers sought medical advice. (4) When a breast-feeding mother requires drug therapy, all available information should be weighed up before advising her to switch to bottle feeding.