The influence of diets containing different types of fat (olive oil or a mixture of 1/3 medium chain triglycerides, 1/3 sunflower seed oil and 1/3 olive oil), and the effect of ursodeoxycholic acid, an exogenous bile acid, on the digestive and metabolic utilization of fat and on the relative percentages of fatty acids in serum in adult rats with 50% distal small intestinal resection and in sham-operated controls three months after surgery has been studied. In resected rats given olive oil as the dietary source of fat, the digestive utilization of fat decreased with respect to controls. Substitution of 1/3 medium chain triglycerides and 1/3 sunflower seed oil for 2/3 of the dietary fat source improved the digestive utilization of fat as judged from the apparent digestibility coefficient, and this improvement was maintained when ursodeoxycholic acid was added to the diet. With both sources of dietary fat tested, intestinal resection led to a decrease in serum levels of triglycerides and cholesterol. However, no significant differences were observed between resected animals fed either type of diet and controls with respect to the relative percentages of fatty acids in serum, saturated and insaturated fatty acid indices or omega 3/omega 6 ratio. The fatty acid profile in serum revealed no deficit in essential fatty acids caused by intestinal resection, type of diet or time, but did reflect clearly the source of dietary fat.