This report describes the results of a Phase II trial designed to evaluate the safety and efficacy of the addition of 1.8 g docosahexaenoic acid each day to an anthracycline-based chemotherapy regimen in Stage IV breast cancer patients. It previously has been shown that cancer cells can be made more sensitive to chemotherapy than non-cancer cells when membrane lipids are enriched with docosahexaenoic acid, a marine omega-3 fatty acid. The study included 25 breast cancer patients with rapidly progressing internal organ metastases who were given 1.8 g docosahexaenoic acid daily, in addition to FEC (5FU, epirubicin and cyclophosphamide), an anthracycline-based chemotherapy regimen. Median overall survival was 22 months. However, median survival reached 34 months in the 12 patients with the highest plasma docosahexaenoic acid. There were no adverse side effects associated with the docosahexaenoic acid.