Delay in the emergence of crawling behavior was observed in a group of seven children. Each was followed from a state of total locomotor immobility to skilled creeping and crawling. Despite the remarkable (up to 1 year) retardation, the pattern of emergence of crawling was generally consistent with that described by McGraw for normally developing children. A notable exception was the tendency of delayed children to begin forward locomotion before they could raise their abdomens off the supporting surface. This finding, taken together with the fact that the most significant delay was found in two anatomically intact individuals who had suffered massive environmental deprivation, suggests that the emergence of typical patterns of prone progression is dependent on adequate very early somesthetic stimulation