In order to study the effects of supplementation of a commercial probiotics product to the diets containing moldy corn, two experiments were conducted with day old male broiler chickens raised in the batteries. Moldy corn was prepared in the laboratory by adjusting moisture content to 20% and incubating at 30-35℃ and 75% relative humidity over 3 weeks. Dried moldy corn was included in the Moldy corn diets at the level of 10%. In the Exp.1, supplementation of probiotics or propionic acid did not significantly affect the performance of chickens fed either Fresh corn or Moldy corn diets. In the Exp.2, supplementation of probiotics significantly (P $lt;0.05) increased cummulative feed intake and weight gain of the brids fed Moldy corn diet at 2 wks of age. Also, supplementation of probiotics significantly (P $lt;0.05) increased cummulative feed intake of the birds fed Fresh corn diet at 5 wks of age. Results of 6 wks feeding trial of Exp. 2 showed that supplementation of probiotics increased weight gain by 5.5% in Moldy corn diet and 3.3o in Fresh corn diet. The weights of abdominal fat pads of the birds fed Moldy corn diets tended to be higher than those of the birds fed Fresh corn diets. Populations of coliform bacteria in the content of lower small intestine were greater in the birds fed Moldy corn diets than those fed Fresh corn diets. Supplementation of probiotics to Moldy corn diets decreased population of coliform becteria. Metabolizabilities of crude fat of Moldy corn diets were significantly (P$lt;0.01) lower than those of Fresh corn diets. Supplementation of probiotics to Moldy corn diet significantly (P$lt;0.01) increased metabolizability of crude fat. Supplementation of probiotics tended to increase metabolizability of crude protein in both Fresh corn diets and Moldy corn diets. Overall results indicated that response to the supplementation of the probiotics might be greater in the Moldy corn diets than in the Fresh corn diets.