The pharmacokinetics of benzodiazepines have been studied because these drugs are often given to pregnant mothers and occasionally to neonates. The rate of absorbition is faster in the neonate than in the mother by all routes of administration but the drugs accumulate, the degree being related to gestational age, the more premature the greater the accumulation. There is preferential storage in some organs including the heart. Diazepam and chlordiazepoxide are metabolised to active compounds but oxazepam, nitrazepam and flurazepam are inactivated. Individual susceptibilities are important. These drugs readily pass across the placenta but the teratogenic risk is uncertain. They are also excreted in the breast milk in quantities which justify their withdrawal during breast feeding. On the basis of the findings therapeutic protocol is proposed.