Saturated fat is considered one of the most important dietary components that should be decreased when attempting to lower plasma total cholesterol (TC). However, it has been suggested that stearic acid (18:0) does not increase plasma TC and should not be grouped with other saturated fatty acids: lauric (12:0), myristic (14:0) and palmitic (16:0), (LMP). Red meat contains a high amount of stearic acid, while dairy products are high in the LMP fatty acids. Since both of these food sources make up a significant part of the American diet, knowing the effects of these different fat sources on the plasma total and lipoprotein cholesterol levels relative to one another is important. Eleven males (22 - 35 y) followed three dietary treatments for four weeks each, separated by a two week wash-out period before crossing over and starting the next dietary treatment. The three dietary treatments were: Beef, Dairy, and Olive Oil. All diets were similar in macronutrient components (37% fat, 13% protein, and 50% carbohydrate). The Beef Diet and the Dairy Diet had a P/M/S ratio of 0.4/1.0/1.0 while the Olive Oil Diet had a P/M/S ratio of 0.4/2.0/1.0. The subjects followed a prescribed menu during the experimental diet periods and kept daily food records during both the experimental periods and the wash-out periods. Twelve-hour fasting blood samples were collected every two weeks during the 18 weeks of the study for a total of ten samples. Plasma was analyzed for TC, high density lipoprotein cholesterol (HDL-C), and triglyceride (TG) levels using enzymatic, colorimetric methods. There were no significant changes in any of the plasma cholesterol or lipoprotein measurements during the Beef Diet or the Dairy Diet. Mean plasma TC decreased progressively during the Olive Oil Diet: 186 (± 26) mg/dl at baseline, 178 (± 23) mg/dl after 2 weeks, and 174 (± 30) mg/dl after 4 weeks (p<0.05). The lack of any significant change in plasma cholesterol values for the Beef Diet or the Dairy Diet may have been due to a combination of matching the M/S ratios, and the smaller than anticipated difference in the stearic acid content between the two diets. / M.S.