The document provides 4 tables that list drugs and other chemicals that are transferred into human breast milk. Table 1 lists drugs that are contraindicated during breastfeeding. Table 2 lists drugs that require temporary cessation of breastfeeding. Table 3 lists maternal medications that are usually compatible with breastfeeding. Table 4 lists miscellaneous agents and their possible effects on infants or lactation. The tables are meant to assist physicians in counseling patients about breastfeeding while taking various medications.