Postural control provides the foundation for successful and safe execution of motor tasks and is controlled by somatosensory, visual, and vestibular systems. Although previous research has determined that youth (7-20 years) with intellectual disability (ID) have problems with postural control when compared to neurotypical (NT) youths, less research exist identifying which system(s) (somatosensory, visual) is the main source for these differences. To date, only removal of vision, not somatosensory (proprioceptors and mechanoreceptors) information, has been studied. The goal of this study was to characterize the balance of youths with ID removing vision (eyes open[EO]/closed [EC]) and manipulating somatosensory (standing on firm surface [Firm] or on foam surface [Foam; 30 x 41 x 6 cm foam, Airex® Balance Pad]) while in a two-foot stance. The goal was accomplished by measuring the center of pressure (COP) on a force plate to determine if statistically significant differences existed for the median velocity (MVelocity, mm/sec) of the COP for the four stances. Total median velocity was chosen to determine balance capacity because it has been identified as one of the most reliable parameters. The literature states that smaller values of these parameters imply better balance. Prior to testing the participants performed a trial test in which they were familiarized with the testing method. Thirty-eight youth (10 females, 28 males; group age = 14.4±3.6r) youths with ID (7 with Down syndrome) stood on an ATMI force plate in one of the four stances for 30 seconds. Participants sat for 1-2 minute(s) on a chair to rest between trials. Participants were allowed to sway from the ankle or hip ('ankle strategy' or 'hip strategy') if the participant kept their stance. The data collection order was in two blocks; block A performed on firm surface, Block B on foam mat. Each block was repeated twice and the best 30 second trial (trial with lowest median) was chosen for statistical analysis. An analysis of variance (ANOVA) with post hoc Tukey was performed to determine if differences existed among the medians for MVelocity (mm/sec) EOFirm ECFirm EOFoam ECFoam MVelocity mm/sec 16.8±10 19.8±15.4 22.6±10.6 30.7±12.9 * between each of the 4 stances. Median velocities increased slightly with more challenging stances. Significant higher median velocities were seen for ECFoam when compared to the EOfirm, ECfirm, and EOfoam. The result of this study compliments and extends the literature in that: (1) loss of vision when on firm surface did not have a significant effect on stance stability; (2) EOFoam median velocity was not significantly different than EOFirm or ECfirm; and (3) concurrent removal of vision and the challenging of somatosensory (ECFoam) displayed higher median velocities than the two stances on firm. The results of this study suggest that youth with ID are more dependent on combined visual and somatosensory information than on visual or somatosensory information alone during postural balance. That is, loss of two sources of sensory information (vision and proprioception) is necessary before a significant effect on balance is observed in a bipedal stance. Future research is needed to determine if similar responses are seen in unipedal or tandem stances.