This study was designed to evaluate the change of gross motor function following selective posterior rhizotomy in children with cerebral palsy. In this study, 24 children with cerebral palsy, ranging in age at surgery from 3 to 12 yrears (average 6.9), were selected. They had surgery in which the selective posterior rhizotomy was performed at Yonsei University Medical Center. They were admitted for rehabilitation in the Yonsei University Rehabilitation Hospital between March 1990 to April 1993. This study measured the gross motor changes in subjects both one week prior to surgery and 6 months after surgery. The measurement tool used was the GMFM (gross motor function measure) scale. The total gross motor mean score difference between the pro-operative and 6months post-operative score was 7.91 (p<0.01). Gross motor scores were analysed in each of 88 conditions, lying, sitting, crawling, walking etc. Lying & rolling scores remained unchanged. Improvement was seen in sitting scores (5.95, p<0.01), crawling & kneeling (6.75, p<0.01), standing (14.79, p<0.01), walking. running. jumping (12.33, p<0.01). The greatest improvement was seen in standing scores. The total mean change in GMFM scores before and after surgery showed a greater increase (5.75 higher, p<0.05) in the non-ambulatory group than the ambulatory. According to condition, the non-ambulatory/ambulatory total mean change (pre and 6 mos. post surgery) difference when compared were as follows: lying & rolling: no difference; non-ambulator improved over ambulators in sitting, crawling & kneeling and standing by mean score difference of 11.65 (p<0.01), 10.36 (p<0.05) and 9.78 (p<0.05) respectively. However, in walking·running·jumping, the ambulatory group mean scores were higher by a mean of 2.30. And the most improved outcome (regardless of ambulation status) was found in the below 5 year age group (p<0.05). IQ was not a relevant factor (p>0.05). These results showed that selective posterior rhizotomy combined with intensive post surgery rehabilitation for children with crerbral palsy had a significant effect on gross motor function. However, further studies with long term follow-up and larger sample size should be done to show more definitive results.