Tibial traits were investigated for turkey poults fed on soyabean-meal-based semi-purified diets high in phytate P (2·2 g/kg) with added phytase and inorganic P. Dietary treatments were: (1) 2·7 g non-phytate P (nP)/kg; (2) diet 1 + 1000 U phytase/kg diet; (3) 36 g nP/kg; (4) diet 3+800 U phytase; (5) 4·5 g nP/kg; (6) diet 5+600 U phytase; (7) 6·0 g nP/kg. Added phytase and nP increased (P < 0·006) tibial dry matter, ash weight and content, body-weight gain, feed intake and gain:feed. The Mg and Zn concentrations in the tibial ash were also increased (P < 0·001 and P < 0·09 respectively) by added phytase or nP; tibial P and Ca concentrations tended to be increased. Hypertrophy zone width of the tibial proximal end decreased (P < 0·001), while proliferating zone width, tibial length, and widths at the long and short axes increased (P < 0·003) as phytase and nP were added. The addition of phytase also tended to enlarge the cartilaginous zone width, which was linearly increased (P < 0·05) by added nP. Disorganization scores of the hypertrophy zone and trabecular bone were low, approaching normal (P < 0·05), for turkey poults fed on diets with phytase supplementation, and tibial abnormality scores were linearly decreased (P < 0·001) as nP levels increased (zero score is considered normal). Adding phytase and nP improved the orderliness of development, mineralization and arrangement of cartilage and bone cells, and alleviated the effects of P deficiency on the histological and gross structure of the tibias. Tibial shear stress increased (P < 0·04) as phytase and nP were added. In summary, similar improvements in bone characteristics were achieved for turkey poults fed on a P-deficient diet supplemented with either phytase or nP.