This experiment was conducted to study the effects of two kinds of sodium and calcium bentonite (NaB and CaB) on performance, blood biochemical parameters, carcass characteristics and tibia ash of broiler chickens. Two hundred and sixty day old broilers of male Ross 308 strain were allocated to 5 treatments with four replicatates and 13 broilers in each. The experiment was carried out in a completely randomized design, where the treatments were: control (corn soybean meal based diet); 1% NaB; 1.5% NaB; 1% CaB; and 1.5% CaB. The results showed no significant difference between the experimental groups in starter and grower periods, but feed intake decreased, and feed conversion ratio was improved by adding 1% bentonite to the diet in finisher and total periods (P<0.05). Addition of bentonite to diet had not significant effect on the blood biochemical parameters, carcass characteristicsand tibia ash. The results indicated that the use of each two kinds of bentonite in diets (1%) improved the broiler performance; however addition of 1.5% bentonite had no significant effect. Manuscript profile