We present the case of an 11-year-old girl with cerebral palsy, who developed bilateral spontaneous ankylosis of the hips as a result of heterotopic ossification following hip surgery. This was treated successfully by a combination of surgical excision, single dose radiotherapy and bisphosphonate treatment at five months from the time of the original surgery. A review of the literature shows that a combination treatment can be recommended in severe cases of heterotopic ossification to prevent recurrence. A review of neurogenic heterotopic ossification is presented. (Hip International 2005; 15: 123-7) KEY WORDS: Neurogenic heterotopic ossification, Hip reconstruction, Ankylosis, Cerebral palsy.