Normally developing infants can produce organized alternating stepping patterns long before they stand alone or attempt to walk, if supported upright on a motorized treadmill. The purpose of this study was to examine whether infants with Down syndrome, who begin to walk at a much later age than non-disabled infants, could produced alternating steps in a similar way. Six of the seven 11-month-old infants studied responded to the treadmill stimulus by producing alternating steps. This suggests that the basic neural substrate necessary for upright locomotion is available long before walking occurs in infants with Down syndrome, as it is in normally developing infants. The infants in this study began to walk at an average of 13.3 months after demonstrating the ability to produce treadmill steps.