Parenteral nutrition-associated liver disease (PNALD) is the most prevalent and most severe complication of long-term parenteral nutrition. Its underlying pathophysiology, however, largely remains to be elucidated. The currently approved parenteral lipid emulsions in the United States contain safflower or soybean oils, both rich in omega-6 polyunsaturated fatty acids (PUFAs). Mounting evidence indicates that the omega-6 PUFAs originating from plant oils in these lipid emulsions may play a role in the onset of liver injury. Fish oil-based lipid emulsions, in contrast, are primarily composed of omega-3 PUFAs, thus providing a promising alternative. The authors review the literature on the role of lipid emulsions in the onset of PNALD and discuss prevention and treatment strategies using a fish oil-based lipid emulsion. They conclude that a fish oil-based emulsion is hepatoprotective in a murine model of PNALD, and it appears to be safe and efficacious for the treatment of this type of liver disease in children. A prospective randomized trial that is currently under way at the authors' institution will objectively determine the place of fish oil monotherapy in the prevention of PNALD.