Intellectual disability affects all spheres of people's lives who suffer from it. It lowers the level of intellectual functioning, often stigmatizes, characteristically changing features, and decreases motor performance. Unfortunately, modern medicine cannot cure intellectual disability; however, there is a chance to improve the quality of life of people with mental retardation by means of physical exercises and by enhancing coordination, the quality of gait and efficiency in performing everyday activities. This paper deals with observations of static balance in 40 young females and males with mild Down syndrome, out of which 20 were subjected to a three-month sensorimotor training programme. The participants performed exercises with rehabilitation balls and air pillows twice a week, and the remaining persons constituted a control group. The balance platform test conducted at the beginning of the experiment revealed that the level of static one-legged balance was similar in both groups. A significant difference was noted in the length of the path of the general centre of gravity (COG) and the time frame in which the vertical projection of COG remained within the 13 mm radius circle, between the result of the test conducted under visual control and with the eyes closed, both in the group of the participants performing exercises and the ones who did not do them. After the training sessions the results of both tests improved in the group of the persons subjected to the training programme, however differences between the groups were not statistically significant, apart from the comparison of the time of keeping COG within the 13 mm radius circle at the beginning and at the end of the experiment by the participants who were physically active. Our results lead to a conclusion that exercises with the use of unstable surfaces improve deep sensibility in people with mild mental retardation. (Contains 10 tables.)