This study was undertaken to determine the effects of fish oil supplementation with low dose on the lipid content and fatty acid composition of breast milk. Among 18 lactating women who were exclusively breast-fed their babies, 6 were in control group and 12 were in fish lil groups. The subjects in fish oil groups were supplemented with 1.96g/d or 3.92g/d of fish oil for 2 weeks from 10 to 12 weeks of postpartum. All subjects consumed their usual diet at home. Breast milk samples were collected at the final day of experiment. By fish oil supplementation, the concentrations of triglyceride, cholesterol, free fatty acid and phospholipid as well as total lipid in breast milk tended to increase, but not significant. There was no dose-dependent response. The fatty acid composition of breast milk was not changed by fish oil supplementation. These results suggest that low dose of fish oil supplementation may increase of lipid content, but does not affect on the fatty acid composition of breast milk.