Context The in vivo evaluation of body tissue development on meat production sheep can be used both to identify and select animals with the best characteristics and to make choices regarding marketing the products of these animals. Aims The objective of this work was to evaluate, using computed tomography, the dynamics of body tissue development and composition of male and female Santa Ines sheep in vivo. Methods The carcass tissue evaluation by computed tomography of 38 sheep (21 male and 17 female) was performed after weaning, at the ages of 90, 120, 180 and 300 days. Based on the Cavalieri method, regression equations were generated for estimates of total weight and proportions of bone, muscle and fat. For the Cavaliere method five males and five females were selected at random and in the four times. In the evaluation of the reference points, all the animals of the study were evaluated in the four times (21 males and 17 females). Key results The mean fat weight was highest at 300 days (2.74 ± 0.99 kg) and lowest at 90 (1.88 ± 0.88 kg) and 120 days (1.91 ± 0.83 kg), indicating that the mean fat area increased with age at all the points evaluated. At age 300 days, the females accumulated more fat than the males whereas the proportions of bone and muscle were higher in the males. Conclusions Computed tomography allowed the evaluation of the body tissues of live animals and was efficient at detecting the changes during the growth phase, besides revealing differences in tissue composition between males and females. Implications The in vivo evaluation by computed tomography of body traits on meat production animals can be used both to identify and select animals with the best productive characteristics, allowing advances in sheep meat production.