Objective To compare the effects of adding barley bran flour and a barley oil extract to a fat-modified diet on serum lipids in persons with hypercholesterolemia. Design The basic design of the study was a randomized, 30-day intervention trial: it included a neutral-fiber control group and a 1-week preintervention period for the collection of baseline data. Subjects The subjects were 79 men aad women with hyper cholesterolemia. Subjects had a mean age of 48.2 years, and all completed the study. Intervention All participants were instructed to follow the National Cholesterol Education Program (NCEP) step I diet and were randomly assigned to one of three treatment groups: 20 g added cellulose; 3 g added barley oil extract, or 30 g added barley bran flour. Main outcome measures Total serum cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and very-low-density lipoprotein cholesterol were measured, along with serum triglycerides, before the intervention, at week I, at week 3, and at the end of the intervention. Statistical analyses performed Student's paired t test was used to detect significant changes within each treatment group from baseline to the end of the 30-day intervention. Ln addition, Pearson's correlation coefficients were used to detect significant correlations between the variables measured. Results Addition of barley bran flour significantly (P=.0001) decreased total serum cholesterol (-0.60 mmol/L as did addition of barley oil (-0.50 mmol/L, P=.002) after 30 days of intervention. Similarly, LDL-C decreased 6.5% with addition of barley bran flour (P=.036) and 9.2% with addition of barley oil (P=.003), Total serum cholesterol or LDL-C of the cellulose control group did not decrease significantly over the same period. HDL-C decreased significantly in the cellulose control group and the barley bran flour group (-0.15 mmol/L, P=.012, and -0.15 mmol/L, P=.006, respectively), but not in the barley oil group. Conclusion We conclude that addition of barley bran flour or barley oil enhances the cholesterol-lowering effect of the NCEP step 1 diet in individuals with hypercholesterolemia.