The prevalence of atopic diseases is increasing throughout the Western world, and means of primary prevention are needed to reverse this trend. The role of breast-feeding, the best source of infant nutrition, in protection against atopic disease remains elusive. In this double-blinded, placebo-controlled study of 62 mother-infant pairs, it is shown that administering probiotics to the pregnant and lactating mother increased the immunoprotective potential of breast milk, as assessed by the amount of anti-inflammatory transforming growth factor beta2 (TGF-beta2) in the milk (2885 pg/mL [95% CI, 1624-4146] in mothers receiving probiotics vs 1340 pg/mL [95% CI, 978-1702] in mothers receiving placebo; P =.018). The risk of developing atopic eczema during the first 2 years of life in infants whose mothers received probiotics was significantly reduced in comparison with that in infants whose mothers received placebo (15% and 47%, respectively; relative risk, 0.32 [95% CI, 0.12-0.85]; P =.0098). Maternal atopy was a clear risk factor for atopic eczema in the infant. The infants most likely to benefit from maternal probiotic supplementation were those with an elevated cord blood IgE concentration. Administering probiotics during pregnancy and breast-feeding thus offers a safe and effective mode of promoting the immunoprotective potential of breast-feeding and provides protection against atopic eczema during the first 2 years of life.