Selective dorsal rhizotomy (SDR) has been shown to be an effective treatment for the spasticity of cerebral palsy, but few studies have addressed specifically the side effects of the procedure. A retrospective study was performed to determine the frequency and nature of complications in 158 children who had undergone SDR at British Columbia's Children's Hospital from 1987 to 1996. Intraoperative, preoperative (immediate postoperative until discharge at approximately 7 days) and postdischarge complications occurred in 3.8, 43.6 and 30% of patients, respectively. The most common intraoperative complication was aspiration pneumonia, which was experienced by 2 patients (1.3%). Perioperatively, sensory changes were found in 8.9% of the children, and transient urinary retention in 4.4%. Complications after discharge included back pain starting more than 6 months after surgery in 10.8%, sensory changes in 13.9%, and neurogenic bladder or bowel problems in 12.7%. Persistent sensory changes occurred in 3.8%, were not important functionally, and tended to occur in patients with the largest amount of dorsal root tissue cut. In 8 patients (5.1%), bladder and/or bowel dysfunction attributed to the SDR was present at the latest follow-up, although in only 2 patients (1.3%) this dysfunction was a definite complication of the rhizotomy. The use of pudendal monitoring and/or cutting less than 50% of the S2 roots may have been associated with a lower incidence of long-term sphincter dysfunction. Data about the nature and frequency of complications may result in further modifications to the SDR procedure, and is critical for counseling about SDR and alternative options available for treatment of the child with spastic cerebral palsy.