Two hundred and eighty-eight 3-week-old mixed-sex broiler chickens were randomly divided into three dietary treatment groups and fed diets containing 0, 100 or 200 g/kg of dietary enzyme, respectively, for four weeks. Feed and water were supplied ad libitum. The parameters studied included growth rate, feed consumption, feed conversion ratio, carcass evaluation, and the economics of production. The addition of dietary enzyme significantly reduced feed consumption (P<0.05); on the other hand, feed conversion efficiency and growth rate improved significantly with increasing levels of enzyme incorporation (P<0.05). The reduction in feed intake compared with birds on the control diet ranged from approximately 10 to 15%. At seven weeks of age, birds on the 100 g/kg and 200 g/kg enzyme were respectively 1.9 and 5.8% heavier than their counterparts on the diet with no added enzyme. Birds fed diets containing the highest level of enzyme were 21.1% more efficient in converting feed to body constituents. Carcass dressing percentage increased significantly with added enzyme (P<0.05). Dietary enzyme significantly decreased the total cost of feed per bird and the cost per kg gain. Enzyme added at 200 g/kg diet was the most economical.