Small intestinal fatty acid synthesis is increased in diabetic rats. Several studies have demonstrated that intestinal triglyceride production and secretion are increased in diabetic animals and may contribute to the hypertriglyceridemia that accompanies diabetes. There are three potential sources of fatty acids for intestinally derived triglycerides; de novo fatty acid synthesis, circulating free fatty acids, or dietarily derived fatty acids. Prior data have demonstrated that de novo cholesterol synthesis is increased in the small intestine of diabetic animals. The primary aim of the present study was to determine the effect of diabetes on small intestinal de novo fatty acid synthesis. We found that de novo fatty acid synthesis in the small intestine is increased approximately 2-fold in streptozotocin-induced diabetic rats. In contrast, hepatic fatty acid synthesis is decreased in the diabetic animals. The increase in intestinal fatty acid synthesis is observed in both the fed and fasting states. Limiting food intake by pair feeding prevents the diabetic-induced increase in small intestinal fatty acid synthesis, a finding similar to previous data on cholesterol synthesis. Thus, the increase in both small intestinal cholesterol and fatty acid synthesis is dependent on the increased food intake that accompanies poorly controlled diabetes. The present study indicates that increases in small intestinal de novo fatty acid synthesis in diabetic animals could play an important role in providing fatty acids for increased small intestinal triglyceride synthesis and secretion. 