Most commonly used drugs are relatively safe for breastfed babies. The dose received via milk is generally small and much less than the known safe doses of the same drug given directly to neonates and infants. Drugs contraindicated during breastfeeding include anticancer drugs, lithium, oral retinoids, iodine, amiodarone and gold salts. An understanding of the principles underlying the transfer into breast milk is important, as is an awareness of the potential adverse effects on the infant. Discussion with the mother about the possibility of either negative product information or ill-informed advice from others will reduce the confusion and anxiety that may be generated. Good resources about medicines and breastfeeding are available and include state-based medicines information services.