A 21-year-old man suffered from diffuse low back pain and sciatica for 10-s periods once or twice a day over a period of 6 months. After this, pain became chronic and was resistant to conventional conservative treatment. Only acetylsalicylic acid diminished pain. Skeletal scintigraphy demonstrated a hot spot at the right side of the fifth lumbar vertebra, and CT scans showed a typical osteoid osteoma in the right pedicle of that vertebra. The time between onset of symptoms and final diagnosis was 18 months. Symptoms disappeared after surgery. Clinical and radiological aspects of the case are discussed.