The acute-phase protein response is associated with accelerated weight loss and shortened survival in cancer. This may be due to hepatic protein synthesis increasing demand for amino acids. An n -3 fatty-acid-enriched nutritional supplement will moderate aspects of cachexia in cancer patients. The present study examined the effect of such a supplement on hepatic synthesis of albumin and fibrinogen. Albumin and fibrinogen synthesis were measured in the fed and fasting state in eight weight-losing patients with pancreatic cancer by an intravenous flooding dose technique. Tracer incorporation into proteins was measured by GC/MS. Patients were restudied after 3 weeks of oral supplement enriched with fish oil (providing 2510 kJ/day and 2 g of eicosapentaenoic acid/day). At baseline, all patients were losing weight (median, 2.4 kg/month). After 3 weeks of consumption of the fish-oil-enriched nutritional supplement, patients' weight stabilized (median change, +1 kg; P = 0.01). At baseline, albumin and fibrinogen synthesis rates were stimulated in the fed compared with the fasting state [14.2 compared with 11.3 g/day (29% rise; P = 0.01) and 4.5 compared with 3.3 g/day (38% rise; P = 0.01) respectively]. After 3 weeks of the supplement, this stimulation in the fed state was no longer observed for albumin and was reduced for fibrinogen [11.2 compared with 10.5 g/day (3% rise; P = 0.21) and 3.7 compared with 2.9 g/day (17% rise; P = 0.01) respectively]. After 3 weeks, the combined albumin plus fibrinogen synthetic rate tended to fall in the fasting state (14.7 compared with 12.3 g/day; P = 0.09) and was significantly reduced in the fed state (18.7 compared with 14.6 g/day; P = 0.01). Modulation of hepatic export protein synthesis with feeding may have contributed to the net whole-body anabolism observed with administration of the n -3 fatty-acid-enriched oral supplement.