Data from the 2001–2004 National Health and Nutrition Examination Survey (NHANES) were used to evaluate serum concentrations of polychlorinated biphenyls (PCBs) in women of reproductive age, with or without a history of breastfeeding. Analytical data for PCBs 138, 153, and 180 were used along with responses to the NHANES Reproductive Health questions: [Have you] breastfed any of your children? ” and “[What] number of children [have been] breastfed [for] at least 1 month? ” PCB concentrations were found to be significantly lower among 15–44 year old women who had a history of breastfeeding compared to those who had not breastfed any of their children. Based on data for 474 women, ages 15–44 years, mean serum PCB 138, 153, and 180 concentrations were 16.4, 21.4, and 14.3 ng/g lipid for women who have a history of breastfeeding, and 24.0, 30.0, and 21.4 ng/g lipid for women who have not breastfed, respectively. These results were weighted using the 2001–2004 sample weights provided by NHANES to represent over 27 million U.S. women. PCB concentrations were also lower among women who had breastfed multiple children. Mean serum PCB 138, 153, and 180 concentrations were 11.8, 15.2, and 10.1 ng/g lipid, respectively, for women 35–44 years who had breastfed six children and 22.7, 31.9, and 22.5 ng/g lipid, respectively, for women 35–44 years who had breastfed only one child. The results tend to support the long-standing hypothesis that depuration of PCBs may occur via breastfeeding.