Sacral plexus injury after radiotherapy for carcinoma of cervix. A 42-year-old woman developed lower extremity weakness and sensory loss 1 year after external and intracavitary radiotherapy for Stage IB carcinoma of cervix. She has been followed for 5 years posttreatment, and the neurologic abnormalities have persisted, but no evidence of recurrent carcinoma has been found. We believe this to be a rare case of sacral plexus radiculopathy developing as a late complication after radiotherapy. Suggestions are made for improving the radiotherapy technique to prevent this complication in future cases. 