Twenty-four 5-day-old male calves were fed twice daily milk replacers containing either 5% (low-fat) or 25% (high-fat) lard. Plasma lipids, blood glucose, and ketone bodies were determined in jugular blood before feeding and every hour during 8 h after feeding. The high-fat diet caused in the 1st h after feeding a sharp increase of triglycerides and phospholipids followed by a sharp decrease; these two increased slowly during the following 5 h. Within the first 2 h after feeding, there was an increase of cholesterol esters, free cholesterol, and nonesterified fatty acids. With the low-fat diet, triglycerides and cholesterol esters showed a small increase during the 4 h following meal whereas phospholipids, free cholesterol, and nonesterified fatty acids were not affected significantly. With both diets, blood glucose reached a maximum of 110 mg/100ml 1 h after feeding; ketone bodies were not altered significantly. With the high-fat diet, lipid digestion would occur in two phases; firstly, part of the fat would be lipolyzed quickly by pregastric esterase before clot formation in the abomasum; secondly, the rest of the lipids, slowly released by progressive lysis of the coagulum would be digested under the action of gastric and pancreatic lipases. The first phase did not occur with the low-fat diet.