Atlantic cod, Gadusmorhua, were maintained on a diet of sandeel and after a 6-day fast were refed a single meal. Concentrations of free amino acids (AAs) were measured in hepatic portal and cardiac blood as well as in the stomach and white muscle at intervals of 6h up to 24h post-feeding. The appearance of both essential and non-essential AAs in the hepatic portal blood was significantly correlated, up to 12h after feeding, to their abundance in the diet. There was a significant decline in total AA concentration in cardiac blood after 6h, followed by a significant increase at 12h. No significant changes in total AA concentration were observed in the other tissues, although mean concentration increased at 12 or 18h. At a more detailed level, the post- prandial changes in concentration of some essential AAs were consistent with their having a role in the stimu- lation of protein synthesis after feeding.