This study was conducted to evaluate the effect of probiotic supplementation on the performance and intestinal microbiota of growing rats. Sprague-Dawley rats, approximately 65.0g, were used to measure body weight gain, feed intake, feed conversion ratio and intestinal pH values and the number of intestinal microorganisms. Experimental diets were prepared as basal diet (C), C + antibiotics (virginiamycin, V), C + live yeast culture (YC) and C + live yeast (LY). Average daily gain (g), daily feed intake (g) and feed conversion ratio of C, V, YC and LY treatments were 3.01, 9.94, 3.30; 3.61, 10.15, 2.81, 3.60, 9.91, 2.75 and 3.43, 9.48, 2.76, respectively. Dry matter digestibility (%) and crude protein digestibility (%) of C, V, YC and LY treatments were 91.75, 84.54, 91.97, 88.56, 93.85, 91.50 and 92.66, 89.99, respectively. The pH values of intestinal contents of C, V, YC and LY treatments in the first week and the fourth week of experiment were 6.45, 6.20, 6,81, 6,78, 7.30, 7.30, 7.40, 7.10, respectively. Colony counts of Lactobacillus were decreased by antibiotic (V) supplementation and increased by probiotics (YC, LY). Colony counts of Coliforms and E Coli were decreased by antibiotic (V) supplementation and increased by probiotics (YC, LY).