The purpose of this study is to evaluate the effects of intramuscular botulinum toxin A injection in cerebral palsy. We studied 25 children with cerebral palsy(age 3 to 20 years old). Among them, 14 children were spastic diplegia; 5 were athetoid quadriplegia; 3 were spastic hemiplegia; and 3 were mixed type(spasticity and athetosis). Botulinum toxin A was injected into the target muscle groups with electromyographic guidance. The dose was calculated in unit/body weight basis. Followup assessments were performed at 1 and 3 months after injection. After injection, 11 out of 16 children(68.8%) had a one-level improvement in ambulatory status. The passive range of joint motion increased significantly after injection. Modified Ashworth scale decreased significantly after injection. In 23 out of 25 children, there were a significant increase of the mean GMFM(gross motor function measure) total score and mean GMFM scores for all dimensions at three months after injection. There were the distant effects after injection in spastic diplegia. In conclusion, botulinum toxin A tretment would improve the motor function and ambulatory status in cerebral palsy by reducing hypertonicity, spasticity, dynamic contracture and athetoid movement.