This review is an update on anesthetic agents and their excretion into breast milk; it presents the reported effects on suckling infants, and discusses the precautions which should be considered. For most anaesthetic agents, there is very sparse information about breast milk excretion and even less published knowledge about the possible effects on the suckling infant. Generally, when an anaesthetic agent is given on a single-dose basis, there is no evidence that it is excreted in breast milk in clinically significant amounts, even if there are detectable concentrations of the drug in the milk. Most anaesthetics are rapidly cleared from the mother, and, consequently, it should be possible to allow suckling as soon as practically feasible after surgery. However, repeated administration of certain opiates and benzodiazepines has been reported to cause adverse effects in neonates, with premature neonates apparently being more susceptible. Thus, in long-term treatment with these drugs, the importance of uninterrupted breast feeding should be assessed against possible adverse drug effects in the neonate.