SummaryGlucose is usually chosen as the energy source for total parenteral nutrition. However, the optimal glucose: fat ratio for peripheral parenteral nutrition has not been examined sufficiently. We compared glucose: fat ratios in hypocaloric nutrition. Male SD rats were given hypocaloric parenteral nutrition (approx. 190kcal/kg/d) for 5 d after laparotomy. The hypocaloric solutions used contained 0, 33, 50, 67 or 100% of the non-protein energy in the form of fat. Body weight change, nitrogen balance, organ weights, and hepatic, splenic and plasma biochemistries were assessed. Body weight increase in the 67 and 100% fat groups was significantly greater than that in the 0% fat group. Ni trogen balance was the same in all groups. Hepatic glycogen content was significantly lower in the 100% fat group than that in the 0% fat group. The weight of epididymal fat deposits was significantly lower in the 0% fat group than in the 50 and 67% fat groups. On the other hand, tissue triglyceride content and plasma lipid levels in the 100% fat group were significantly higher than in the 0% fat group, and were also higher than in the control group. It is suggested that combinations of glucose and fat have sparing effects on body fat and hepatic glyco gen. Combinations of glucose and fat as non-protein energy sources were superior to glucose or fat alone for hypocaloric parenteral nutrition. Key Words rat, peripheral parenteral nutrition, laparotomy, glucose, fat emulsion Peripheral parenteral nutrition (PPN) has been developed for reasons of safety, simplicity and cost. The use of PPN avoids certain disadvantages seen in total paren teral nutrition, such as complexity of technique and catheter-related sepsis (1, 2). However, PPN also has disadvantages such as thrombophlebitis, which is a serious problem (3) and limits the amount of energy that can be supplied. The causes of thrombophlebitis are thought to be the pH (4), osmolarity (5) and titratable acidity (6) of the solution. To avoid increases in the osmotic pressure of the solution and provide energy sources effectively via the peripheral vein, fat emulsions are frequently 47