Prognosis of locomotion in children with cerebral palsy (CP) is complicated by the variety of motor and other neurologic deficits in each case. Children presenting with spastic diplegic (SD) CP related to prematurity generally demonstrate more uniform and comparable neuromotor abnormalities. In this study, longitudinal data were collected on the early postural-locomotor development of children with spastic diplegic cerebral palsy (SDCP). The data were then correlated with the level of ambulatory function attained. Fifty spastic pediatric patients, aged 5 to 19 years, were included in the study completed in 1982. The duration of follow-up ranged from 4 to 16 years. The study is based upon a method of assessing preambulatory milestones, a classification of ambulatory function into four levels of ability, and correlates these two sets of data. The results indicate that the motor control of sitting and crawling at 1 1/2 to 2 1/2 years was predictive of the eventual level of ambulatory function the child was able to attain and maintain.