The factors associated with failed operative intervention in the treatment of equinovarus foot deformity in children with cerebral palsy (CP) were evaluated after long-term follow-up. One hundred eight children with CP who had surgery on the posterior tibialis tendon (split tendon transfer, intramuscular lengthening, or Z-lengthening) on 140 feet were reviewed at a mean age of 16.8 years with 7.3 years of follow-up. The surgery was considered a failure when a 10 degrees or greater varus or valgus hindfoot deformity was present or if an additional operative intervention was required or planned. Involvement of CP, age at operation, and preoperative status of ambulation were significant factors in the outcome of the surgery. Hemiplegic patients demonstrated the best results, regardless of age or surgical procedure. Seventy-five percent of diplegic and quadriplegic patients who were younger than 8 years or who were not capable of community ambulation failed operative intervention, and surgery on the posterior tibialis tendon is not recommended in this group of patients.