Twelve men consumed a basal diet containing 14.6% of the calories as protein, 35.0% as fat (P/S = 0.39, 641 mg cholesterol), and 50.4% as carbohydrate for 20 wk. Four refined fibers, cellulose, carboxymethylcellulose gum, locust bean gum, or karaya gum, were added to the basal diet individually for 4 wk each at the level of 0.75 g fiber/100 cal. Total serum cholesterol and plasma low-density lipoproteins decreased significantly after carboxymethylcellulose gum, locust bean gum, and karaya gum were consumed for 4 wk compared to levels after the basal diet alone. No change was observed in triglyceride, very low-density lipoprotein or high-density lipoprotein cholesterol levels. The high-density lipoprotein/very low-density lipoprotein + low-density lipoprotein cholesterol ratio after feeding carboxymethylcellulose gum was significantly higher than the ratios after cellulose or the basal diet. These results indicate addition of these gums in the amount of 0.75 g fiber/100 cal to a basal diet lowers serum cholesterol without decreasing the high-density lipoprotein cholesterol, resulting in a higher high-density lipoprotein/very low-density lipoprotein + low-density lipoprotein cholesterol ratio in circulation, significantly higher when the diet contained carboxymethylcellulose gum.