The purpose of this study was to investigate the changes in electromyographic (EMG) patterns after multilevel surgical treatment in children with spastic cerebral palsy. Children with diplegia (n=18) and hemiplegia (n=16) aging from 6 to 16 years participated in the study. Twenty healthy children within the same age span are presented as reference. Gait analysis and surface electromyograms of seven major lower limb muscles were assessed before and 1-5 years after the multilevel surgery. The most frequent procedures were equinus correction, distal rectus femoris transfer, femoral derotation osteotomy and hamstrings lengthening. The results showed that the EMG pattern of the soleus, lateral gastrocnemius and tibialis anterior muscles became closer to normal after the surgery, while no differences were detected between diplegic and hemiplegic patients. Furthermore, a subgroup of 10 patients showed an increase in medial hamstrings activation during preswing that decreased postoperatively. These findings indicate that changes in EMG patterns should not be ruled out after surgical treatment, although the extent of these changes is limited compared to changes in the kinematics. Abnormal muscle activation before the operation can be related to a compensatory response in some patients and this can be manipulated after surgery.