The purpose of this study is to evaluate the effectiveness of intramuscular botulinum toxin A injection in cerebral palsy with foot deformities using roentgenogram. We have studied 26 children with cerebral palsy(age 3 to 13 years old). They were twenty spastic diplegias, three hemiplegias and three mixed types(spasticity and athetosis). The botulinum toxin A was injected into gastrocnemius or peroneous muscles with an electromyographic guidance. Before injections, passive joint angles of the ankle were assessed by the goniometric measurements. A plantar-flexion angle of talus, dorsiflexion angle of calcaneous, and talar-calcaneal divergence angle were measured using the lateral and anterior-posterior roentgenograms of the foot with weight- bearing for the assessment of equinovalgus of ankle. Follow-up assessments were performed at 1 and 3 months after the injection. At 1 month after the injection into gastrocnemius muscle, there was an increased range of passive ankle joint motion, decreased plantar-flexion angle of talus, and increased dorsiflexion angle of calcaneous. These changes were still significant at 3 months after the injection. After the injection into peroneous muscle, the talar-calcaneal divergence angle was significantly decreased. This study provides the evidence that the treatment with botulinum toxin A improves the ankle joint motion in cerebral palsy with feet deformities by reducing hypertonicity, spasticity and dynamic contracture. In addition, the lateral and anterior- posterior roentgenograms of the foot with weight bearing seems to be the simple and objective methods to evaluate the effectiveness of intramuscular botulinum toxin A injection in cerebral palsy with foot deformities.