The objective of this study was to explore the influence of a series of simple triglycerides and natural fats on cholesterogenesis and lipogenesis. Male rats were given a partially synthetic diet containing no added fat or 30% of tributyrin, tricaproin, tricaprylin, tricaprin, trilaurin, trimyristin, tripalmitin, triolein, trilinolein, lard, butter oil, safflower oil, or a synthetic triglyceride made of one part palmitic and two parts oleic acids. After 2 weeks, the rats were administered 0.2 mc. acetate-1-C14/kg. of body weight (intraperitoneally) and were sacrificed 1 hr. later. Various tissues were removed for analysis. When compared to the low fat diet, all of the non-linoleic acid diet fats caused increases in liver 16:1 and 18:1 acids at the expense of the polyene acids, mainly 18:2 and 20:4. Stearic acid was also reduced in all cases except after tricaprin and triolein. In addition to the above, the tripalmitin diet compensated for a pronounced loss in the polyunsaturated acids with an increase in the 16:0 and 18:0 acids. Unexpectedly, dietary laurate was not deposited in the liver but resulted in a larger increase in liver myristate than after the ingestion of myristate itself. The animals on the low fat diet incorporated over 7% of the labeled acetate into liver fatty acids, those on the short-chain fat diet about 5%, those on the medium chain length fat diet 2.5%, those on the longer chain length saturated fat diet 1.5%, and those on the safflower oil and trilinolein diets only 0.3 and 0.2%, respectively. During the ingestion of the short-chain fatty acids, a very high level of palmitic acid synthesis occurred, suggesting that the short-chain acids do not inhibit its synthesis and are themselves converted to palmitic to a significant degree. During the ingestion of the long-chain fatty acids, all synthesis of fatty acids was strongly inhibited. In all cases there was a lower degree of incorporation of acetate into oleic than into palmitic. The concentration of liver cholesterol was only 2.3 mg./g. in animals on the low fat diet, approximately 4–5 mg./g. in animals on the saturated triglyceride diets, about 6 mg./g. in those on the triolein diet, and above 7 mg./g. in those on the trilinolein diet. However, only tripalmitin ingestion increased the level of liver cholesterol synthesis, as measured by the percentage of injected labeled acetate incorporated. Two weeks of dietary tripalmitin sharply decreased the amount of newly synthesized cholesterol transported into the aorta during the first hour after labeled acetate injection.