The purpose of this study was the morphometric assessment of the metacarpal III bone in and the estimation of Ca (calcium) and P (phosphorous) contents in the dorsal cortical of the mid left diaphysis of left metacarpal III bone in crossbreed with criolla-mare. The metacarpal III bones of 30 young mares betwen two and five years old were studied and the samples were grouped according to age. The sample groups were: younger than 2 years old (G1); between 2-3 years old (G2), between 3-4 years old (G3), and betwen 4-5 years old (G4). The contents of Ca and P in the bones were determined by X-spectometry. The mean lengths of the right and left metacarpal III were 24, 07 cm and 24,05 respectively. The total area, the cortical area and the medullar area in the mid of the right and left diaphysis were 8.01 cm_ and 7.98 cm_; 6.63 cm_ and 6.58 cm_; 1.37 cm_ and 1.40 cm_, left and right respectively. The mean distribution of Ca and P in all age groups was higher in the mid-third of the cortex dorsal from left metacarpal III were: G1:61.88 and 39.98; G2: 44.54 and 32.99; G3:62.39 and 47.50 and G4:46.83 and 32.64, for the Ca. and P respectively. The mean distribution of the mean value of Ca and P has been in the middle third. In the metacarpal of the mare from the second year of age until the fifth year of age, cortical continuous remodelling occurs. This remodelling affects its morphometric bone and the Ca and P contents