Treating psychiatric disorders with pharmacotherapy in the breast-feeding period presents a dilemma as such treatment carries the risk of infant exposure to medication through breast milk. However, failure to institute pharmacotherapy in postnatal women in need of such treatment exposes both mother and baby to detrimental effects of the illness. Because women presenting with psychiatric disorders during the postpartum period often have complex sets of symptoms, monotherapy may not be sufficient for symptom resolution. In this case series of 6, we examined levels of psychotropic medications secreted in breast milk and performed developmental assessments of the exposed babies with the Bayley Scales of Infant Development, Second Edition. In 3 of the 6 cases, no medication was detected in the breast milk; in all but 1 case, estimated levels of infant medication exposure were calculated to be less than 0.01 mg/kg per day for each medication. Four of the 6 babies scored as being within normal limits on the Bayley Scales of Infant Development, Second Edition, whereas 2 showed mild developmental delays. In comparison to the 4 cases of typical development, the 2 showing mild delays did not have higher estimated levels of psychotropic medication exposure through breast milk. Based on these results, in our limited sample, there appears to be low levels of infant exposure to the medications through breast milk; no association was seen between developmental outcomes and exposure through breast milk of multiple pharmacological agents. These results should be interpreted with caution, and vigilance should be exercised when advising women on combinations of medications for severe mental illness who choose to nurse.