The objectives of this study were to screen the possible effects of B. subtilis and its soluble byproducts against C. perfringens, a causative agent of necrotic enteritis (NE) in chickens. The use of B. subtilis strain was found to be inactive in vitro against C. perfringens but its cell filtrate byproducts produced after growth of B. subtilis at 37°C with medium pH adjusted at 5.0, having inhibitory effect in the form of inhibitory zones; measured inhibition of 12 mm. The produced anticlostridial factor was not affected by heat treatment at 70, 100 or 121°C for 15 minutes. The study recorded the responses of broiler chickens to oral administration of C. perfringens and the possible antagonistic effects of B. subtilis and its cell-free filtrate byproducts in vivo. Results revealed that B. subtilis decreased the severity of intestinal necrotic lesions produced after oral inoculation of C. perfringens and the suggested anticlostridial effect was more clear when the cell- free filtrate produced by growing B. subtilis at 37°C with pH 5.0 was added to feed at a dose of 20 ml/kg of ration.