An experiment was carried out to determine the effects of different levels of natural zeolite and calcium (supplied by calcium carbonate and dicalcium phosphate) on performance, apparent digestibility of calcium and tibia ash on 480 Ross male broiler chicks. Eight experimental diets were tested in a factorial arrangement with four levels of zeolite (0, 1, 2, and 3 percent) and two levels of calcium (NRC recommended level, and 70 % of NRC level) with completely randomized design with 5 replicates and 12 chicks per replicate. The results indicated that with adding zeolite to diet, feed consumption were reduced in grower and whole period of the experiment (P<0.05), but there were not significant difference between control diet (0 % zeolite), and the diet containing 1 percent of zeolite. Adding zeolite to diets improved feed conversion ratio, not significantly. Use of zeolite in diets had no significant effects on carcass percentage, apparent digestibility of calcium, and tibia ash content, but increased relative abdominal fat content (P<0.05). With decreasing calcium level, feed consumption were increased, but weight gain and feed conversion ratio decreased in grower period (P<0.05). Decreasing calcium level in diets reduced carcass percentage, and tibia ash content significantly (P<0.05). Interaction between zeolite and calcium on tibia ash content was significant (P<0.05).

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