An oat bran concentrate was prepared by removing non-fibre components by cold-water wet-milling, resulting in a 2- to 3-fold concentration of soluble fibre, with beta-D-glucan as its main component. The concentrate was baked in bread which was consumed for 8 weeks by free-living men with mild to moderate hypercholesterolaemia. The effects on serum lipids were assessed in a randomized, double-blind, placebo-controlled trial. Despite the large daily dose (11.2 g) of beta-glucan, the beta-glucan-enriched bread had only a small and statistically non-significant effect on serum lipid concentrations. Probable reasons for the weakness of the effect could be the poor solubility of beta-glucan in the preparation, its enzymatic hydrolysis after ingestion, and the consequently low viscosity in the intestine.