The influence of various levels of supplemental phytase on P and Ca availability was investigated using morphometric indices and the bone strength of tibiotarsi in broilers. Forty tibiotarsi were used from the Ross 308 male broilers fed corn-soybean meal based diets. Dietary treatments were: 1) Control: diet with DCP, 2) Negative control: control diet without DCP, 3) Control diet + 300 U of phytase/kg, 4) Control diet + 500 U of phytase/kg, 5) Control diet + 700 U of phytase/kg. There were no significant differences among the groups in the mean for tibiotarsal weight and length and also for the thickness of the medial wall. However, 300 U/kg diet with phytase supplementation had a greater influence on the tibiotarsal weight/length index and the robusticity index when compared to those of broilers in both control groups, and the thickness of the lateral wall and tibiotarsal index among all the groups (P<0.05). The percentages of tibia ash were improved by the addition of dietary phytase. Phytase supplementation slightly improved tibia breaking stress and the modulus of elasticity in broilers. Increasing phytase levels from 300 to 700 U of phytase/kg of diet provided no additional benefits for tibiotarsal bone characteristics and strength in broilers.