Beta-glucans are glucose polymers present in cereal grains, particularly barley and oat. Consumption of these grains or concentrated beta-glucan preparations has been shown to lower blood cholesterol. The present study was conducted to assess the safety of a high purity (>75%) barley beta-glucan (Glucagel™). The product was fed to Wistar rats (5/sex/group) at dietary levels of 0% (control), 1%, 5% and 10% for 28 days. Clinical and neurobehavioural observations, growth, feed and water consumption, ophthalmoscopy, haematology, clinical chemistry, urinalysis, organ weights, necropsy and histopathological examination revealed no adverse effects of Glucagel™. High-dose males exhibited lower plasma cholesterol and phospholipids levels and a higher plasma urea level. These slight changes were considered of no toxicological significance. Full and empty caecum weights were increased in mid- and high-dose males. This caecal enlargement was a physiological response to the consumption of a high amount of indigestible carbohydrate and considered of no toxicological concern. In conclusion, feeding Glucagel™ at dietary levels up to 10% for 28 days was tolerated without any signs of toxicity. This dietary level was equivalent to 7.7 g Glucagel™ (5.8 g beta-glucan)/kg body weight/day in male rats and 7.8 g Glucagel™ (5.9 g beta-glucan)/kg body weight/day in female rats. © 2009 Elsevier Ltd. All rights reserved.