Depression is one of the most common psychiatric disorders. A variety of different chemical structures have been found to have antidepressant activity. The number is constantly growing; however, as yet, no one group has been found to have a clear therapeutic advantage over the others. The major indication for antidepressant drugs is depression, but a number of side effects have been established by clinical experience and controlled trials. It is clear that, to some extent, any drug or chemical substance administered to the mother is able to cross the placenta unless it is destroyed or altered during metabolism. Placental transport of maternal substrates to the fetus and of substances from the fetus to the mother is established at about the fifth week of fetal life. Traditionally, teratogenic effects of antidepressants or other drugs have been noted as anatomic malformation. It is clear that these are dose- and time-related and that the fetus is at great risk during the first 3 months of gestation. However, it is possible for antidepressants to exert their effects on the fetus at other times during pregnancy as well as to infants during lactation. Administration of antidepressants to pregnant women presents a unique problem for the physician. Not only must maternal pharmacologic mechanisms be taken into consideration when prescribing an antidepressant drug, but the fetus must also be regarded as a potential recipient of the drug. Certain results are evident with regard to drugs administered during lactation. It is essential that physicians need to be aware of the results of animal studies in this area and of the potential risk of maternal drug ingestion to the suckling infant.