This paper is a review of the main psychomotor characteristics of kids with fragile X syndrome. Almost all the boys and 30% of girls affected present mental retardation from the first year of life. At the psychomotor level basic activities such as crawling, walking on all fours, walking or running, and their subsequent psychomotor disability are mainly caused by hypersensitivity to sensorial inputs and difficulties in sensorial processing, low muscular tone and joint hyperflexibility or stiffness, difficulty in movement planning and coordination, inefficient motor control, low proprioceptive and vestibular integration and lack of balance. Other characteristics are described: hyperactivity and stereotypies. Due to space restrictions, the article does not go into the emotional-social relationship involved in psychomotor intervention.