Male's diameter of an internal carotid artery increases to teenage in the left internal carotid artery, by the youthful period - in the right internal carotid artery, then remains stable throughout all individual development of an organism. Female person's diameter of an internal carotid artery increases by the period of the second childhood, stabilizes till the mature period. Authentic sexual distinctions on an indicator of diameter of internal carotid arteries, since the period of the early childhood are revealed.

Key words: internal carotid arteries, ontogenesis, sex.