In order to investigate the effects of feed restriction and starvation on the fatty acid synthesis and the oxidation of glucose and alanine to CO₂ in the hepatopancreas of carp Cyprinus carpio, the fish were fed a commercial diet at feeding rates of 100%, 50%, and 0% (starvation) ofsatiation for 30 days. The rate of fatty acid synthesis from D-[U-14C] glucose and L-[U-14C] alanine, theactivities of lipogenic enzymes, and the levels of serum triglyceride and body lipid were decreased by feed restriction and starvation. Moreover, the rate of glucose oxidation together with the glycolytic enzyme activities was significantly low in starved fish. However, the rate of alanine oxidation was scarcely changed, and alanine was more actively oxidized to CO₂ than glucose regardless of feeding rate. Theseresults indicate that the fatty acid synthesis and glycolysis are depressed by feed restriction including starvation and suggest that amino acids are the major energy sources for the hepatopancreas regardless of feeding rate.