Alcohol consumption is linked to increased breast cancer risk. Since oestrogens increase breast cancer risk, possibly through oxidative damage, and we have shown that alcohol consumption increases serum oestrogens, we tested whether moderate alcohol supplementation increased oxidative DNA damage among healthy postmenopausal women not on hormone replacement therapy in a randomized controlled crossover study. We used serum 5-hydroxymethyl-2-deoxyuridine (5-HMdU) autoantibodies (aAbs) as a marker of oxidative DNA damage. The results showed no evidence for increased or decreased levels of oxidative DNA damage among women who consumed 15 g or 30 g alcohol per day for 8 weeks compared with women in the 0 g alcohol group. We conclude that among healthy women, it is possible that an 8-week trial of moderate alcohol supplementation might be too short to make enough 5-HMdU aAbs to compare differences by alcohol dose. In future studies, a panel of biomarkers for DNA damage should be used.