The impact of reduction mammoplasty surgery on breastfeeding performance was measured comparing a group of 49 Brazilian women who had undergone breast reduction surgery using transposition techniques with 96 controls. As determined by survival analysis, the women who underwent reduction mammoplasty had a significantly shorter time of breastfeeding duration. The prevalence of exclusive breastfeeding at 1 and 4 months was 21% and 4%, respectively, for women with surgery, and 70% and 22%, respectively, for controls (P < .001). The prevalence of any breastfeeding at 1, 6, and 12 months was 58%, 16%, and 10% for women with mammoplasty, and 94%, 58%, and 42% for controls (P < .001). For women with surgery, the median duration of exclusive and any breastfeeding was 5 days and 2 months, respectively, and 3 months and 6 months for controls. The results of this study suggest that breast reduction surgery may have a negative impact on breastfeeding performance.