This study was designed to determine whether developmental changes occur in the duration and quality of maintaining a prone extension position. Three groups of 26 to 30 normal children ages 4, 6, and 8 years were tested on the prone extension position. Results indicated a significant difference in both duration of maintenance and quality between the performance of the four-year-olds and the other two age groups. No significant differences were found between the six- and eight-year-olds. Smooth assumption of the position and distance of thighs off the mat were found to be the most important factors in discriminating a good prone extension position from an inadequate one. The variability of performance by the four-year-olds indicates that the ability to assume and maintain a prone extension position is not a valid measurement tool for discriminating between normal children and those “at risk” for learning disabilities at this age level. The inability of children six years or older to maintain a “good” prone extension position for 30 seconds suggests a vestibular processing inefficiency.