A 24-year-old man with persistent low back pain and right sciatica, was found to have an osteoid osteoma of the right pedicle of the second lumbar vertebra. 99mTc-MDP bone scan and CAT scan produced an early diagnosis of the lesion. Intraoperative 99mTc-MDP in vitro combined with imaging and quantitative activity measurements were useful for accurate localization and complete removal. The method is simple and can be performed in every nuclear medicine department, with no need for special operating room facilities.