Non-starch polysaccharide (NSP) content of barley is predominately in the form of β-glucan, whereas in wheat it is predominately pentosans (containing the sugars arabinose and xylose). It has generally been accepted therefore that a high level of β-glucanase is needed in broiler diets containing barley, whereas wheat based diets require a high level of endoxylanase. Trials have however previously suggested that including an endoxylanase based enzyme in broiler diets will perform at least as well as enzyme containing highlevels of β-glucanase in diets containing up to 30% barley. To confirm this finding, a trial was initiated at Roslin Institute, Edinburgh to compare the effectiveness of Natugrain Blend 66% (an endoxylanase based product) against Natugrain 33% (endoxylanase/β-glucanase product) in diets containing up to 30% barley.