Postpartum blues occurs in 50-80% of women. A few percent of the cases are classified as serious postpartum depression, requiring antidepressant treatment. There is a growing understanding that women should continue to breast-feed in this situation. Data concerning the transfer of antidepressants into breast milk has been researched. Calculations of the infant relative dose via breast milk were done for the drugs concerned. Few antidepressants have been studied at steady state conditions in nursing mothers. Nortriptyline and amitriptyline have minimal relative doses and can be used when breast-feeding. Doxepine should be avoided, as should lithium, which has a significant transfer. Among the serotonine-reuptake inhibitors fluoxetine has been well studied in breast milk. Since fluoxetine has a long half life and a high transfer, sertraline and possibly paroxetine are better alternatives, but the latter has not yet been studied in repeated doses. Moclobemide also lacks data from multiple dose studies, but extrapolation to steady state indicates that the relative dose is small. More observational studies should be carried out in infants breast-fed by mothers using antidepressants. In the meantime, doctors prescribing antidepressant drugs to nursing mothers should see that the infants are monitored for side effects.